A fiber structure includes a blank portion formed as a single part by three-dimensional weaving between a first plurality of yarn layers and a second plurality of yarn layers, the blank portion corresponding to all or part of a fiber reinforcement preform for a part made of composite material. Outside the blank portion, the fiber structure includes one or more two-dimensional fabric layers, each two-dimensional fabric layer grouping together the yarns of a single layer belonging to at least the first plurality of yarn layers and situated outside the blank portion.