Centrally rotating sweeping auger (10) for a circular silo (1) for the storage of agricultural products such as cereals or grains, comprising an auger endless screw (20) and a casing portion (29.1, 29.2, 29.3, 29.4, 29.5) that is fixed relative to the auger screw, partially enveloping the auger endless screw so as to leave free access for the agricultural products to the auger endless screw on one side of the screw through an opening (200.2, 200.3, 200.4, 200.5) between the fixed portion of the casing and the floor of the silo. According to the invention, the casing comprises at least one cap (30) that is mobile with respect to the fixed portion of the casing, between a retracted position in which the opening is uncovered and a deployed position in which the cap covers the opening.
