A crushing mill for crushing fibrous material for a unit for forming absorbent cores in a machine which makes absorbent sanitary articles, including a casing having an infeed opening and an outfeed opening for the fibrous material, a rotor rotatable about its axis of rotation and housed in the casing at an intermediate position between the infeed opening and the outfeed opening. Also provided is an auxiliary opening operatively interposed between the infeed opening and the outfeed opening, with reference to a direction of rotation of the rotor, and adapted to allow feeding a particulate absorbent material into an intermediate zone between the infeed opening and the outfeed opening.