A method and an apparatus for establishing whether fiber material is contaminated with foreign objects is characterized in that for the finding of foreign objects in the form of foreign fibers and pieces of foil, for example packaging remnants such as jute sack remnants, plastic foil remnants, cords or bands, rags or cleaning scrim, the fiber material delivered in bales is investigated during bale opening. The investigation takes place by scanning the surface of at least some of the layers of fiber material exposed during the bale opening, and the degree of the contamination with the scanned foreign objects is retained and is stored in association with the particular bale which has been scanned.