A method is disclosed for forming a two-compartment bag. The method comprises draping a sheet of bag forming material around a primary fill pipe and one or more secondary fill pipes, forming multiple compartments by sealing the sheet material around the respective fill pipes, filling the various compartments with material, and sealing the bag.The method comprises forming transverse seals so that a transverse seal area of a secondary compartment at least partially overlaps with a transverse seal area of the first compartment, so that the secondary compartment is fixedly folded against the first compartment.The method permits the volume of the secondary compartments to be varied independent from the volume of the primary compartment. Each compartment may be opened without opening the other compartments.In a preferred embodiment the bag is made of a microwave-compatible material, and at least one of the compartments contains a food material intended for reheating or preparation in a microwave oven.
