Document:

<PAGE>

                                                                     EXHIBIT 4.3

SECOND CLARIFICATIONS MEMORANDUM FOR MIXED FINANCED PUBLIC WORKS CONTRACT
(CONTRACT NUMBER PIF-005/2003) DATED MARCH 26, 2003, WHICH IS ENTERED INTO BY
AND BETWEEN COMISION FEDERAL DE ELECTRICIDAD ("COMMISSION") AND CONSTRUCTORA
INTERNACIONAL DE INFRAESTRUCTURA, S.A. DE C.V. (THE "CONTRACT").

      COMMISSION AND CONSTRUCTORA INTERNACIONAL DE INFRAESTRUCTURA, S.A. DE C.V.
("CONTRACTOR", AND JOINTLY WITH COMMISSION, THE "PARTIES") WISH TO ISSUE THE
FOLLOWING CLARIFICATIONS REGARDING THE CONTRACT REFERRED TO IN THE HEADING OF
THIS MEMORANDUM WHICH THEY EXECUTED ON MARCH 26, 2003. TERMS BEGINNING WITH A
CAPITAL LETTER SHALL HAVE THE MEANINGS THERETO ATTRIBUTED IN THIS CONTRACT,
UNLESS EXPRESSLY OTHERWISE PROVIDED FOR HEREIN.

      1. The Parties make it clear that for the "VO" calculation under Exhibit
14 of the Contract, the value of the Works contracted both at a lump sum as at
unit prices shall be adjusted to present value per the date of early termination
or rescission of the Contract, and for such calculation the future date
considered shall be 60 Days after (i) the Scheduled Acceptance Date of the First
Unit (February 28, 2007) in respect to 60% of such value, and (ii) The Scheduled
Completion Date of the Project (August 31, 2007) in

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                                        2

respect to the remaining 40%, in the means such dates are (a) delayed in virtue
of a delay attributable to Contractor; or (b) adjusted due to an Act of God or
of Force Majeure, or (c) in case of an extension of those dates according to
clauses 13.3 and/or 27.3 of the Contract. On the other hand, and without
prejudice of Contractor's rights according to clauses 26.5 and 27.4 of the
Contract, in case of extensions of Dates of Critical Events attributable to
Commission according to Clause 13.3 of the Contract or a Major Government Force,
the latter shall pay for reasonable financial costs according to practice in the
market, - duly documented -, derived from the actual delay in the Critical Event
Dates per the date of early termination of the Contract, as long as those costs
are not included in amounts paid or due on account of start-up delay insurance;
for the calculation of those financial costs, they shall be considered to result
once the 60-Day term stipulated in Clause 26.5 of the Contract has expired, and
based on the financial cost derived from financing amounts actually disbursed by
Contractor before the date of early termination.

      2. The Parties make it clear that the Monthly Progress Report referred to
in Clause 13.4 and item 4 of the First Clarifications Memorandum may be issued
in two bimonthly Progress Reports for each Month, in which case the

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                                        3

provisions of such Item 4 shall be applicable to each of those bimonthly
Progress Reports in relation to the monthly Progress Report.

      3. In relation to Exhibit 14 of the Contract, the Parties make it clear
that, if any Works are not in similar conditions to those of the date when the
respective recognition was granted because of a deterioration that affects their
adequate operation, to avoid duplicating charges Commission shall invoke
paragraph (c) of Exhibit 14, as long as the amount(s) of the deterioration
suffered is (are) not included in item "S" of Exhibit 14 because of the
insurance Contractor must have according to Clause 24 of the Contract. It is
also made clear that item "S" of Exhibit 14 does not include amounts paid or due
for start-up delay insurance, as such insurance does not cover physical damage
of the Works.

      4. In relation to the monthly Progress Reports established in Clause 13.4
of the Contract, the Parties make it clear that Contractor may include in those
Reports amounts actually disbursed during the period covered by the
corresponding Report on account of pre-operating non-recoverable expenses
required to execute the Project, the value whereof must have documentary support
validated and endorsed by the Supervision Resident for Commission to

<PAGE>

                                        4

recognize amounts still not amortized in the corresponding Report as actual
progress, according to the procedure and for the purposes established in Item 4
of the First Clarifications Memorandum. Aforementioned concepts will be the same
as those consigned in forms OE-2, OE-9A, OE-16.4, OE-16.5, OE-16.6, OE-16.12 of
Contractor's Bid.

      5. The Parties make it clear that the term sanction in Clause Seven of the
Modifying Contract of the Contract, executed July 4, 2003, refers both to the
obligation to pay the contract penalties and to deliver an additional letter of
credit according to the last paragraph of Clause 13.6.1 of the Contract; neither
may default of the date mentioned in aforementioned Clause Seven constitute an
Event of Default by Contractor.

      This Clarifications Memorandum forms an integral part of the Contract. It
consists of 2 (two) written pages and is signed in five original copies in
Mexico, Federal District, on October 8, 2003.

FEDERAL ELECTRICITY COMMISSION
(illegible signature)
________________________________
EUGENIO LARIS ALANIS
INVESTMENT PROJECTS DIRECTOR

CONSTRUCTORA INTERNACIONAL DE
INFRAESTRUCTURA, S.A. DE C.V.
(illegible signature)

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                                        5

________________________________
LUIS HORCASITAS MANJARREZ
Legal Representative<PAGE>

                                                                     EXHIBIT 4.4

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)

AMENDING AGREEMENT TO THE FINANCED PUBLIC WORK MIXED CONTRACT NO. PIF-005/2003,
ENTERED INTO BY AND BETWEEN COMISION FEDERAL DE ELECTRICIDAD, REPRESENTED HEREIN
BY EUGENIO LARIS ANALIS, ENGINEER, ACTING AS DIRECTOR - FINANCED INVESTMENT
PROJECTS, ON ONE HAND, AND THE CORPORATION CONSTRUCTORA INTERNACIONAL DE
INFRAESTRUCTURA, S.A. DE C.V., REPRESENTED HEREIN BY JORGE BERNARDO AGUIRRE
QUINTANA, ENGINEER, ACTING AS THE ATTTORNEY AT FACT THEREOF, ON THE OTHER,
HEREINAFTER DENOMINATED "THE COMISION" AND "THE CONTRACTOR", RESPECTIVELY, IN
ACCORDANCE WITH THE FOLLOWING STATEMENTS AND CLAUSES:

                                   STATEMENTS

I.-   THE PARTIES state that:

I.1   On March 26, 2003, they celebrated the Financed Public Work Mix Contract
      recorded under No. PIF-005/2003, legal instrument that will be referred
      hereinafter as the "Contract", awarded to THE CONTRACTOR by means of the
      International Public Bid procedure stipulated in Articles 27, Item I, 28
      and 30 item II, 32, 33 and 45 of the Public Works and Related Services Law
      and which object consists of: "the execution of Public, Electromechanical
      and Associated Works, procurement, engineering, manufacture,
      transportation, assembly, tests and commissioning of two equipped
      turbogenerator Units, with a 375 MW nominal power rating each, for the
      specified design drop and volume of flow detailed in Section 8 of the
      Bidding Conditions, Works which as a whole are called El Cajon
      Hydroelectric Project, which main structures are located in the
      municipalities of Yesca and Santa Maria del Oro, State of Nayarit, United
      Mexican States."

      The works consisting in the Lump-Sum Price Activities are described in
      detail in the Section 4, exhibits OE-3, OE-4, AND OE-5 of the Bidding
      Conditions and will be carried out on a lump-sum price mode basis, while
      the part of the Works corresponding to the Unit Price Activities are
      described in detail in the Section 4, exhibit OE-5A of the Bidding
      Conditions and will be executed on a unit price basis.

I.2   The Contract Price Sum agreed upon in Clause 9.1 was arranged as total
      payment for the performance of the Works corresponding to the Lump-Sum
      Price Activities

Translator's Note: At the foot and right margin of this and every sheet
constituting this instrument several illegible signatures are subscribed, except
for the signatures page.

<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)

      amounting to US$ 682' 517, 584.80 (Six hundred eighty two million five
      hundred seventeen thousand five hundred and eighty four dollars 80/100 US
      Cy) and for the Unit Price Activities, THE COMISION shall pay to THE
      CONTRACTOR the sum of US$ 65' 773, 072.59 (Sixty five million seven
      hundred and seventy three thousand seventy two dollars 59/100 US Cy), plus
      the respective value added tax.

I.3   The starting and development according to the Works Execution Schedule was
      duly agreed in clause 13.1 of the Contract, according to which THE
      CONTRACTOR was obliged to initiate the works on March 26, 2003 and to
      complete them by August 31, 2007, being the term for the execution of
      Works 1620 Days.

I.4   The stated Contract is ruled by the Public Works and Related Services Law
      in accordance with Clause 31.1 of the Contract.

I.5   In agreement with the provisions of articles 59 of the Public Works and
      Related Services Law and 69 and 79 of its Regulations, it is herein
      stipulated that the Entities may, within its authorized Investment
      Schedule they are in charge of and due to grounded and explicit reasons,
      amend the mixed public works contracts in the part corresponding to unit
      prices by means of agreements, provided that these, considered either
      jointly or severally, neither go beyond 25% of the amount or term agreed
      under the Contract nor imply material variations to the original project
      or are celebrated in order to evade, in any way, the compliance with the
      Law or the Treaties.

I.6   Clause 9.3 of the Contract provides that "...THE COMISION may request THE
      CONTRACTOR to perform the additional works in relation to the Unit Price
      Activities up to 25% of the Contract price or more, subject to the
      stipulated in the Public Works and Related Services Law corresponding to
      the unit price mode, by means of the celebration of an agreement, at any
      time, previous the Temporary Acceptance of the related Unit, provided that
      the additional works are not included in the scopes of the Contract and
      their object is neither to amend nor repair omissions or materially modify
      the contracted project and provided that it is duly grounded and motivated
      that technically, the execution of those additional works was
      unforeseeable and that they are required for the completion and operation
      of the project."

II.-  THE COMISION states that:

II.1  The need to amend the original contract was determined and, therefore, the
      celebration of this amending agreement is required due to the following
      reasons, detailed in the exhibit 1 of the present agreement:
<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)

   1. Due to the lack of timely delivery by THE COMISION of the real estate
      where works covered by the present Contract will take place in view of the
      lack of Access to the Site, as a result of the delay in the building of
      the access road to El Cajon Hydroelectric Project, delays not imputable to
      THE CONTRACTOR have been experienced, that affected the Execution
      Schedule, which jointly with the days required for the execution of the
      additional and extraordinary works, according to the Technical Opinion,
      which is an integral part of this agreement as Exhibit No. 1, endangers
      the completion of the Diversion Works for July 1, 2004 the thus the Final
      Closing that would cause the deferment of the commissioning of Units.

   2. According to the stated in the previous paragraph, it is necessary to
      analyze the actual affectation of the work schedule in order to allow as
      far as possible, the meeting of the dates originally agreed upon.

   3. Derived from the considerations comprised in the Technical Opinion, same
      that justifies the celebration of the present legal instrument, THE
      COMISION has resolved: the need to increase the amount of the Contract
      exclusively on the unit price portion according to the provisions of
      clause 9.1; to modify the Starting Date stipulated in clause 13.1; the
      original Execution Schedule; and the Critical Events Dates stated in the
      Exhibit 3 of the Contract according to the stipulated in clause 13.3,
      grounded on the provisions of articles 59 of the Public Works and Related
      Services Law and 69 and 79 of its Regulations.

   4. The execution of the present agreement takes place in order that the Site
      is available for THE CONTRACTOR as well as the proper conditions to have
      access thereto.

   III.-    THE CONTRACTOR states that:

   III.1    It is acquainted with the scope of the amendments subject matter of
            the present agreement, that it has legal capacity and enough
            elements to comply with them.

   Due to the previously stated, THE PARTIES grant the following:

                                     CLAUSES

   FIRST.-  THE PARTIES agree that the object of the present Amending Agreement
            consists of: (i) increasing the amount of Contract exclusively in
            the portion of Unit Price Activities referred to in clause 9.1 and
            exclusively derived from the following Additional and extraordinary
            works: exterior work in the entrance gates to the diversion tunnels,
            including excavations, sewerage
<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)

            works and treatments; removal of material resulting from the
            excavations carried out, same that was deposited by other
            contractors in the area adjacent to the Gates; and Construction of
            the Cantiles I Bridge at km. 41+733 of the access road, which detail
            is attached hereto as Exhibit 2, (ii) agreeing on the execution
            schedule for the Additional and Extraordinary Works herein
            described, and (iii) the commitment by THE PARTIES to analyze and
            conciliate a new Execution Schedule and the defacing of Critical
            Events Dates set forth in the Exhibit No. 3 of the Contract, derived
            from the modifications to the contracting conditions that have been
            stipulated up to date under clause 13.1 and by the execution of the
            Additional and Extraordinary Works herein mentioned.

   SECOND.- It is THE PARTIES will to agree that, in view of the works carried
            out by third parties and related to the object of the present
            Amending Agreement, from this act THE CONTRACTOR is released from
            any liability derived from hidden vices, poorly executed works,
            which repair is not the object of the present Agreement or the
            non-compliance with the Applicable Laws.

   THIRD.-  THE COMISION and THE CONTRACTOR agree on extending the original
            amount of the portion of the contract unit prices by the amount of
            US$ 5' 801, 271.26 (Five million eight hundred one thousand, two
            hundred and seventy one dollars 26/100 US Cy), being consequently
            the total amount of the portion of the contract unit prices US$ 71'
            574, 343.85 (Seventy one million five hundred seventy four thousand
            three hundred and forty three dollars 85/100 US Cy) plus the related
            value added tax, according to the budget of the Additional and
            Extraordinary Works which, as an integral part of this agreement is
            included as Exhibit No. 2, representing an increase of 8.82% (eight
            point eighty two percent) with respect to the Contract related Unit
            Price part.

   FOURTH.- The monthly advance payments of the concepts covered by this
            Agreement shall have the same acknowledgement treatment and payment
            terms stipulated in the Contract for the Unit Price Activities under
            clauses 9.2, 10.1 and 13.4.

   FIFTH.-  THE PARTIES agree that the works of the Additional and Extraordinary
            Works subject matter of this Agreement shall be executed from May 3,
            2003 to August 15, 2003 for the entrance and exit gates of the
            diversion tunnels and the Cantiles I bridge will be executed from
            May 13, 2003 to August 30, 2003; the previously stated is evidenced
            in the monthly schedule of amounts that is included as an integral
            part of this Agreement in the Exhibit No. 3. Upon the completion of
            each one of these Additional and Extraordinary
<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)

            Works, THE COMISION will acknowledge it separately and definitively
            according to the Exhibit 14 of the Contract, this means, as it if
            were an event of advance acknowledgement comprised in the economic
            form OE-11B.

   SIXTH.-  In view of the agreed in the precedent clauses and due to the lack
            of timely delivery by THE COMISION of the real estate where the
            works covered by the Contract will be executed, resulting from lack
            of Access to the Site, due to the delay in the building of the
            access road to the Site, the new works starting date is April 24,
            2003; in view of the previously stated, the Works starting date
            stipulated in clause 13.1 "Starting and Development According to the
            Execution Schedule" is modified; likewise, THE PARTIES grant their
            consent herein so that the original Execution Schedule and the
            Critical Events Date are analyzed, conciliated, modified and
            formalized by means of an Amending Agreement to be celebrated
            subsequently, among which the date of the following Critical Events
            of the Exhibit 3 of the Contract will be adjusted in the first
            place:

            1.1   Starting of excavation of diversion tunnels.

            1.2   River diversion; and

            1.3   Starting of the construction of the access tunnel to the
                  engine house.

            According to the set forth in the previous paragraph and in the
            Statements II.1.1 and II.1.2, THE PARTIES agree that within the 30
            Days period from the date of execution of the present Agreement they
            shall define the technical alternative and the Additional Works
            necessary which, as far as possible, will allow the meeting of the
            dates originally agreed in the Execution Schedule. The new work
            schedule and its associated costs, as well as the dates of the
            Critical Events, shall be duly documented by means of an Amending
            Agreement.

 SEVENTH.-  THE PARTIES agree on the following:

            The sanction of the Critical Event subject to Penalty corresponding
            to Item 1.4 "Completion of the construction of upwards and downwards
            water cofferdam" of Exhibit 3 of the Contract is invalid according
            to the Official Letter No. DPIF/289/2003 dated June 18, 2003.

 EIGHTH.-   THE PARTIES agree that the amount of the Compliance Bond granted by
            THE CONTRACTOR for the equivalent to ten percent (10%) of the
            investment amount authorized for the first fiscal year is enough to
            secure the due, proper and full compliance by THE CONTRACTOR with
            all its
<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)

            obligations derived from the Contract and the present Agreement for
            the present fiscal year, since the Works Execution Schedule
            originally agreed upon has been affected as stipulated in clause
            First and Sixth above.

  NINTH.-   The celebration of the present Agreement neither means waiving the
            rights acquired by THE CONTRACTOR, derived from the lack of the
            delivery of the site under the terms stipulated in the Bidding
            Conditions and in the Contract nor any other situation previous to
            the execution of the present Agreement.

            THE CONTRACTOR acknowledges that the celebration of this Agreement
            only satisfies all its rights for the Additional and Extraordinary
            Works described in the Exhibit 2, waiving thus to any present claim
            that is not expressly stipulated in this Agreement, resulting from
            the same cause that gave rise thereto.

  TENTH.-   THE PARTIES agree that except as expressly stipulated in the terms
            of the present Agreement, each and all other clauses integrating and
            constituting the Contract shall survive and rule it with its full
            force and legal scope.

The terms capitalized in the present Agreement and not expressly defined herein
shall have the same meaning assigned to them in the Clause 1.1 of the Contract.

IN WITNESS WHEREOF, THE PARTIES celebrate and grant the present Agreement by
means of their signatories duly authorized in six counterparts which shall be
equally valid in Mexico City, Federal District, this July 4 of the year two
thousand and three.

BY THE COMISION                                     BY THE CONTRACTOR

ILLEGIBLE SIGNATURE                                  ILLEGIBLE SIGNATURE
EUGENIO LARIS ALANIS, ENG.                 JORGE BERNARDO AGUIRRE QUINTANA, ENG.
DIRECTOR - FINANCED                                  ATTORNEY AT FACT
INVESTMENT PROJECTS

Exhibit 1.-       Technical Opinion.
Exhibit 2.-       Additional and Extraordinary Works.
Exhibit 3.-       Additional and Extraordinary Works Monthly Amounts Schedule.
Exhibit 4.-       Causes justifying the legal basis of the Agreement.

<PAGE>

Translator's Note: On the left lower margin three signatures are subscribed.

<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)
                                                                   EXHIBIT NO. 4

CAUSES JUSTIFYING THE LEGAL BASIS OF THE AMENDING AGREEMENT NO. 1 TO THE
FINANCED PUBLIC WORK MIXED CONTRACT NO. PIF-005/2003, ENTERED INTO WITH
CONSTRUCTORA INTERNACIONAL DE INFRAESTRUCTURA, S.A. DE C.V., IN RELATION TO THE
EXECUTION OF CIVIL, ELECTROMECHANICAL AND ASSOCIATED WORKS, PROCUREMENT,
ENGINEERING, MANUFACTURE, TRANSPORTATION, ASSEMBLY, TESTS AND COMMISSIONING OF
TWO EQUIPPED TURBOGENERATORS UNITS WITH A 375 MW NOMINAL POWER RATING EACH, FOR
THE SPECIFIED DESIGN DROP AND VOLUME OF FLOW DETAILED IN SECTION 8 OF THE
BIDDING CONDITIONS, WORKS WHICH AS A WHOLE ARE CALLED EL CAJON HYDROELECTRIC
PROJECT, WHICH MAIN STRUCTURES ARE LOCATED IN THE MUNICIPALITIES OF YESCA AND
SANTA MARIA DEL ORO, STATE OF NAYARIT, UNITED MEXICAN STATES.

1.-   That on March 26, 2003, they celebrated the Financed Public Work Mixed
      Contract, recorded under No. PIF-005/2003, legal instrument that will be
      referred hereinafter as the "Contract", awarded to THE CONTRACTOR by means
      of the International Public Bid procedure stipulated in Articles 27, Item
      I, 28 and 30 of the Public Works and Related Services Law and which object
      consists of: "THE EXECUTION OF PUBLIC, ELECTROMECHANICAL AND ASSOCIATED
      WORKS, PROCUREMENT, ENGINEERING, MANUFACTURE, TRANSPORTATION, ASSEMBLY,
      TESTS AND COMMISSIONING OF TWO EQUIPPED TURBOGENERATOR UNITS, WITH A 375
      MW NOMINAL POWER RATING EACH, FOR THE SPECIFIED DESIGN DROP AND VOLUME OF
      FLOW DETAILED IN SECTION 8 OF THE BIDDING CONDITIONS, WORKS WHICH AS A
      WHOLE ARE CALLED EL CAJON HYDROELECTRIC PROJECT, WHICH MAIN STRUCTURES ARE
      LOCATED IN THE MUNICIPALITIES OF YESCA AND SANTA MARIA DEL ORO, STATE OF
      NAYARIT, UNITED MEXICAN STATES."

2.-   Under the terms of Clauses 9.1, 9.3 and 13.1 of the Contract it was agreed
      as total payment for the execution of the works corresponding to the
      Lump-Sum Price Activities, being THE COMISION obliged to pay to THE
      CONTRACTOR, the amount of US$ 682' 517, 584.80 (Six hundred eighty two
      million five hundred seventeen thousand five hundred and eighty four
      dollars 80/100 US Cy) and for the Unit Price Activities, THE COMISION
      shall pay to THE CONTRACTOR, US$ 65' 773, 072.59 (Sixty five million seven
      hundred and seventy three thousand seventy two dollars 59/100 US Cy), plus
      the respective value added tax. That in

Translator's Note: At the foot and right margin of this and every sheet
constituting this instrument several illegible signatures are subscribed, except
for the signatures page.

<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)
                                                                   EXHIBIT NO. 4

      relation to the starting and development according to the Works Execution
      Schedule, THE CONTRACTOR was obliged to initiate the works on March 26,
      2003 and to complete them by August 31, 2007, being the term for the
      execution of Works 1620 Days.

3.-   In accordance with Clause 31.1.- Applicable Law.- THE PARTIES agree that
      the present Contract shall be ruled and construed in accordance with each
      and all the clauses constituting it, as well as with the terms,
      guidelines, procedures and requirements stipulated in the Public Works and
      Related Services Law and its Regulations and all other Federal Laws of
      Mexico.

4.-   The mentioned Contract is ruled by the Public Works and Related Services
      Law in agreement with the provisions of articles 59 of the Public Works
      and Related Services Law and 69 and 79 of its Regulations; the Entities
      within its authorized Investment Schedule they are in charge of and due to
      grounded and explicit reasons, may amend the mixed public works contracts
      in the portion corresponding to unit prices by means of agreements,
      provided that these, considered either jointly or severally, neither go
      beyond 25% of the amount or term agreed upon under the Contract nor imply
      material variations to the Original Project or are celebrated in order to
      evade, in any way, the compliance with the Law or related Treaties.

5.-   In order to initiate the works entrusted to THE CONTRACTOR subject matter
      of the Contract, Additional and Extraordinary Works were ordered besides
      those considered in the bidding conditions, resulting in that additional
      works not originally foreseen were carried out, same that are fully
      detailed in the technical opinion (exhibit No. 1 of the present Agreement)
      comprising grounded and explicit reasons supporting the granting of the
      present agreement; these additional works are not included in the scopes
      of the Contract and their object is neither to amend nor repair omissions
      or materially modify the contracted project and the execution of those
      additional works was unforeseeable, and they are required for the
      completion and operation of the project."

These are the causes justifying the formulation of the Amending Agreement No. 1
(ONE) to extend the amount of the Contract in the portion corresponding to the
Unit Price Activities in an amount of US$ 5' 801, 271.26 (Five million eight
hundred one thousand, two hundred and seventy one dollars 26/100 US Cy) plus the
related value added tax.

<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)
                                                                   EXHIBIT NO. 4

BY THE COMISION                                       BY THE CONTRACTOR

ILLEGIBLE SIGNATURE                                   ILLEGIBLE SIGNATURE
EUGENIO LARIS ALANIS, ENG.                 JORGE BERNARDO AGUIRRE QUINTANA, ENG.
DIRECTOR - FINANCED                                    ATTORNEY AT FACT
INVESTMENT PROJECTS

Translator's Note: On the left lower margin three signatures are subscribed.

<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)
                                                                   EXHIBIT NO. 1

TECHNICAL OPINION INCLUDING THE GROUNDED AND EXPLICIT REASONS JUSTIFYING THE
LEGAL BASIS OF THE AMENDING AGREEMENT TO THE TO THE FINANCED PUBLIC WORK MIXED
CONTRACT NO. PIF-005/2003, DATED MARCH 26, 2003, ENTERED INTO WITH CONSTRUCTORA
INTERNACIONAL DE INFRAESTRUCTURA, S.A. DE C.V.

ANTECEDENTS

1.- On September 3, 2003 started the International Public Bid No.
18164093-011-02, by means of the publication of the public call for bid No.
005-2002 for the execution of El Cajon Hydroelectric Project, located in the
municipalities of Yesca and Santa Maria del Oro, State of Nayarit, United
Mexican States, called by THE COMISION Federal de Electricidad for the Awarding
of a Financed Public Work Mixed Contract for the Construction of Civil Works of
a concrete face rock-fill dam, electromechanical works and associated works,
procurement, assembly engineering, transportation, tests and commissioning of
two equipped turbogenerator units and with guaranteed values of power rating at
several hydraulic drops, which under design conditions and as a whole will not
have a power rating o less than 750 MW (in the power transformer high voltage
terminals.)

      According to the several proposals of the bidders, in the already
mentioned International Public Bid procedure that took place on February 7 and
March 14 of this year, respectively, the holding of the contract was awarded to
the corporation Constructora Internacional de Infraestructura, S.A. de C.V.
determining that the execution of the work would comprise a term from March 26,
2003 to August 31, 2007, where it was also stipulated that the awarded company
would obtain all the necessary financing for the execution of the Works and the
completion of the Project.

2.- As a result of the delay in the execution schedule of the excavation works
of the entrance and exit gates of the diversion tunnels and the construction of
the Cantiles I Bridge that would allow the delivery to THE CONTRACTOR, in the
conditions consigned in the Bidding Conditions regarding the Works site, the
Construction General Resident Engineer's Office of THE COMISION deemed
convenient to suspend the activities of the contracting company responsible for
such works and to request THE CONTRACTOR their execution in order to ensure the
compliance thereof and, in turn, to prepare the conditions so that installations
and the feasible preparations to be ready for the starting of the excavation of
diversion tunnels contracting works included in the Contract could take place
simultaneously. In view of the previously stated and the set forth in the
Official Document No. FSC-343/03 delivered on April 21, 2003, the Construction
General Resident Engineer's Office requested THE CONTRACTOR to contact the
Specific Work Resident

<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)
                                                                   EXHIBIT NO. 1

Engineer in order to receive the diversion tunnels' exit gate on April 23 and 25
for the entrance gate, respectively.

3.- Due to the geological conditions found in the diversion tunnels' exist gate,
on April 24, 2003, THE COMISION delivered to THE CONTRACTOR the modification to
the exit gate design, where gates are displaced 25 and 28 meters, respectively,
for tunnels 1 and 2 in the upstream waters direction.

These extraordinary events modify the design delivered by THE COMISION on the
International Public Bidding Conditions, generating the need to carry out
additional and extraordinary activities not contemplated in the contracting
project originally agreed with THE CONTRACTOR.

4.- During the April 26 - May 7 period both, THE COMISION and THE CONTRACTOR
jointly carried out topography works consisting in the location of supporting
points and cross-section surveys of both gates.

All the previously stated was recorded in the Logs Nos. 11, 12, 13 and 14 dated
May 1, 3, 5 and 8, respectively.

5.- In view of the Cantiles Bridge location, it is an obligated pass to access
the works Site and it is fundamental to ensure its completion before the regular
rainfall period that may endanger the access to the main project works.

6.- The additional resulting costs and the time required to execute the previous
modifications were requested to THE CONTRACTOR by THE COMISION for its due
analysis and revision and, as the case may be, the related incorporation to the
respective Amending Agreement, taking into account the volumes and amounts
corresponding to the Additional Works described in this Technical Opinion and
which are not contemplated in the Execution Schedule originally agreed with THE
CONTRACTOR, consisting of: excavations, sewerage works and treatments in the
diversion tunnel gates, as well as the removal of product material of the
excavations executed, same that was deposited by other contractors in the area
between the entrance and exit gates, as well as the Construction of the Cantiles
I Bridge, at Km 41+733.

7.- It is worth stating that due to the displacement of the diversion tunnels
exit gate, 25 and 28 meters, these tunnels will be cut in such lengths.

<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)
                                                                   EXHIBIT NO. 1

WHEREAS CLAUSES

I.- Seen the technical elements that prevented THE CONTRACTOR to start both, on
time and form its activities at the Site regarding El Cajon Hydroelectric
Project diversion works according to the contracting working schedules, THE
COMISION immediately proceeded to analyze the feasibility that THE CONTRACTOR
may execute the works related to: exterior work at the diversion tunnels gates
including excavations, sewerage works and treatments; removal of product
material of the excavations executed, same that was deposited by other
contractors in the area between the entrance and exit gates, as well as the
Construction of the Cantiles I Bridge; in order to make use of the availability
of THE CONTRACTOR, its capacity of immediate response to carry out these works,
its infrastructure and expertise, since its personnel is at work site, as well
as the machinery and available equipment, besides of its general knowledge of
the Project, being thus convenient for the public interests of THE COMISION that
THE CONTRACTOR executes such works.

II.- Likewise, the resulting benefits from the amendment of the Contract shall
be taken into account in order that THE CONTRACTOR carries out the mentioned
works, since in the first place, it will execute them immediately, which will
result in that THE CONTRACTOR starts the Contract works within a shorter term,
preventing thus the increase of delays and costs overrun in the
physical-financial schedules.

III.- Therefore, these additional and extraordinary works are an integral part
of the obligations of Contract in the part of unit prices from the execution of
the respective Amending Agreement, in accordance with provisions of clause 9.3
of the Contract, Article 59 of the Public Works and Related Services Law and
Articles 69 and 79 of its Regulations, considering that these works are an
integral part of El Cajon Hydroelectric Project even though its contracting was
initially carried out with different contractors and that these are not over 25%
of the amount and term originally contracted.

IV.- Also, THE COMISION considers that the entrusting to THE CONTRACTOR the
additional and extraordinary works previously described will generate for THE
COMISION a more adequate benefit-cost with the obtainment of significant savings
in view of the fact that THE CONTRACTOR widely and conceptually knows the
project, which will allow to cut down time, since should a bidding process
according to the provisions of Public Works and Related Services Law and the
applicable Normativity be implemented, the execution of the Contract works would
be delayed, increasing thus the risk not to put into operation the project
within the foreseen term.

<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)
                                                                   EXHIBIT NO. 1

V.- The budget of the Additional and extraordinary Works delivered by THE
CONTRACTOR has been reviewed, conciliated and validated by THE COMISION, having
determined that it satisfies all the conditions required that will allow the
compliance within the shortest possible time of the construction of the referred
works.

VI.- Likewise, THE COMISION deems convenient the amendment of the Contract both
in its amount and term, since the climate conditions of the region that will
prevail during summer will make it compulsory to execute the additional and
extraordinary works in the shortest possible time, in order to prevent that the
rainfall period hinders the respective works.

Apart from the stated considerations, THE COMISION deems convenient to state the
following:

A).- That on March 26 and 27 of 2003, personnel from the Construction General
Resident Engineer's Office of THE COMISION and THE CONTRACTOR carried out the
tour through the access road and the site of the main and associate structures
to the Work in order to verify their actual status, informing THE CONTRACTOR to
the representatives of the Construction General Resident Engineer's Office about
the arrival of some equipment on March 27, 2003.

B).- In relation to the diversion work gates, THE CONTRACTOR manifested its
interest to agree on the reception of the mentioned fronts (faces) in the
current conditions, in order to execute the additional works that will be
entrusted to it according to the provided in clause 9.3 "Variation of Works and
clause 13.3 item b) "Adjustment of Critical Events Dates".

The previously stated is consigned in the following documents: note of Log No.
2; minutes of kickoff protocol meeting of works subject matter of the Contract;
and agreements included in the Working Minutes identified with the control
number LECAJ 1502 RG1 MTC01.

Due to the above mentioned and in view of the reasons expressed in the present
document, THE COMISION proceeds to issue the following:

OPINION

FIRST.- Grounded on the provisions of articles 59 of the Public Works and
Related Services Law and 69 and 79 of its Regulations and clause 9.3 "Amendments
to the Contract" of the Contract, THE COMISION issues a favorable opinion to
celebrate the

<PAGE>

                        COMISION FEDERAL DE ELECTRICIDAD

                                                       CONTRACT NO. PIF-005/2003
                                                           AGREEMENT NO. 1 (ONE)
                                                                   EXHIBIT NO. 1

present Amending Agreement both, in Time and Amount to the Contract, based on
the whereas clauses stipulated in the body of the present Technical Opinion for
the execution of the additional and extraordinary stated works.

SECOND.- It is ruled that the amount of the additional and extraordinary works
related to the construction of the exterior work of the diversion tunnels gates,
including excavation, sewerage works and treatments, removal of material
resulting from the excavations carried out, same that was deposited by other
contractors in the area between entrance and exit gates and the construction of
the Cantiles I Bridge, will be US$ 5' 801, 271.26 (FIVE MILLION EIGHT HUNDRED
ONE THOUSAND TWO HUNDRED AND SEVENTY ONE DOLLARS 26/100 US CY) and that the
progress and payment certificate shall be those stipulated in the Contract.

THIRD.- It is ruled that the new starting date of Works is April 24, 2003, the
works of Additional and Extraordinary Works subject matter of the Agreement will
be executed from May 3, 2003 to August 15, 2003 for the diversion tunnels
entrance and exit gates and the Cantiles I bridge will be executed from May 13,
2003 to August 30, 2003.

The present Technical Opinion is subscribed in Mexico City, Federal District on
July 2, 2003.

ILLEGIBLE SIGNATURE                                    ILLEGIBLE SIGNATURE
HUMBERTO MARENGO MOGOLLON, PhD                 BENJAMIN GRANADOS DOMINGUEZ, ENG.
COORDINATOR-HYDROELECTRIC                      ASSISTANT DIRECTOR-PROJECTS
PROJECTS                                       AND CONSTRUCTION

                               ILLEGIBLE SIGNATURE
                           EUGENIO LARIS ALANIS, ENG.
                     DIRECTOR - FINANCED INVESTMENT PROJECTS

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