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                                                                     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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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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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

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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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________________________________
LUIS HORCASITAS MANJARREZ
Legal Representative