A resealable bag is formed of flexible sheet material having, embedded therein, a number of parallel, spaced apart strips of inelastic but bendable material which are capable of assuming a set position when bent. The strips, which extend generally longitudinally along the full length of the bags, each include a substantially widened portion, near the mouth of the bag, which co-operates with the flexible package walls to form a closure for resealing the package. A series of filled bags may be formed by first forming a continuous length of a flexible two-ply sheet material having a number of strips disposed between the plies. The end of the sheet is drawn past a hollow mandrel so as to bring the sheet edges into overlapping relation. The overlapped edges are joined to form a tube, the end of which is sealed with a transverse seam to form an open-ended bag. The open bag is then filled through the mandrel, sealed with a transverse seam and severed from the length of material.