A freezing mould bag including: two sheet-like film pieces (12, 14) having substantially the same geometrical shape and defining an outer, substantially rectangular periphery with two sides, a bottom and a top; a peripheral joint (20, 21, 21a, 21b) extending along the greater part of the outer periphery of the film pieces with the exception of a peripheral area at the top for establishing a filling opening of the bag, the peripheral joint joining the film pieces with each other substantially overlapping each other and delimiting an inner compartment of the interior of the bag, the inner compartment constituting at least one freezing mould compartment, preferably a plurality of interconnected freezing mould compartments which are delimited in relation to each other by separate joints (22, 23, 24, 25) of the film pieces; a filling duct delimited by separate joints (30, 32) of the film pieces and extending from the inner compartment of the bag to the filling opening such that access from outside to the inner compartment of the bag is achieved via the filling opening; two closing valve flaps (16, 18) connected by the film pieces (12, 14) at the filling opening and extending from the filling opening into the interior of the bag towards the inner compartment of the bag along the filling duct, the closing valve flaps being joined with each other and joined with the film pieces via the separate joints (30, 32) delimiting the filling duct such that two closing pockets that open towards the inner compartment of the bag are provided; wherein the joints at the freezing mould compartment or freezing mould compartments at one or both sides of the filling duct are broken for establishing communication with an expansion chamber formed at one or both sides of the filling duct, and which is delimited by further joints of the two film pieces (12, 14); and wherein at a position at each side of the filling duct and over the inner compartment of the bag there is formed a material weakening of the superposed film pieces for establishing a severing; characterised in that the material weakenings of the superposed film pieces (12, 14) for establishing a severing runs from the side edge at an angle relative to a joint delimiting the adjoining freezing mould compartment or compartments to a position near the mouth of the filling duct in the inner compartment, in that along the filling duct there is left an unbroken joint whereby the expansion chamber or chambers are formed in the areas between the material weakening, the side edges and the joints at the freezing mould compartment or compartments. two sheet-like film pieces (12, 14) having substantially the same geometrical shape and defining an outer, substantially rectangular periphery with two sides, a bottom and a top; a peripheral joint (20, 21, 21a, 21b) extending along the greater part of the outer periphery of the film pieces with the exception of a peripheral area at the top for establishing a filling opening of the bag, the peripheral joint joining the film pieces with each other substantially overlapping each other and delimiting an inner compartment of the interior of the bag, the inner compartment constituting at least one freezing mould compartment, preferably a plurality of interconnected freezing mould compartments which are delimited in relation to each other by separate joints (22, 23, 24, 25) of the film pieces; a filling duct delimited by separate joints (30, 32) of the film pieces and extending from the inner compartment of the bag to the filling opening such that access from outside to the inner compartment of the bag is achieved via the filling opening; two closing valve flaps (16, 18) connected by the film pieces (12, 14) at the filling opening and extending from the filling opening into the interior of the bag towards the inner compartment of the bag along the filling duct, the closing valve flaps being joined with each other and joined with the film pieces via the separate joints (30, 32) delimiting the filling duct such that two closing pockets that open towards the inner compartment of the bag are provided; wherein the joints at the freezing mould compartment or freezing mould compartments at one or both sides of the filling duct are broken for establishing communication with an expansion chamber formed at one or both sides of the filling duct, and which is delimited by further joints of the two film pieces (12, 14); and wherein at a position at each side of the filling duct and over the inner compartment of the bag there is formed a material weakening of the superposed film pieces for establishing a severing; characterised in that the material weakenings of the superposed film pieces (12, 14) for establishing a severing runs from the side edge at an angle relative to a joint delimiting the adjoining freezing mould compartment or compartments to a position near the mouth of the filling duct in the inner compartment, in that along the filling duct there is left an unbroken joint whereby the expansion chamber or chambers are formed in the areas between the material weakening, the side edges and the joints at the freezing mould compartment or compartments.