Sunderland are investigating claims that a Sheffield United player was struck by a bottle thrown from the stands during Saturday's Sky Bet Championship clash between the sides.
The Black Cats have confirmed they are aware of the allegation and are awaiting the outcome of an investigation into events at the Stadium of Light.
It is understood referee Jeremy Simpson, who picked up what appeared to be a plastic bottle and handed it to the fourth official, has indicated that he will include the incident in the report he submits to the Football Association.
Deadline-day signing Clayton Donaldson appeared to be struck by the bottle as he celebrated his second goal of the game against the Black Cats.
The club are reviewing CCTV footage in an effort to identify whoever threw the object.
Sunderland slipped to 20th place in the table as a result of a 2-1 defeat with Donaldson scoring both goals for the Blades before Jack Rodwell's late reply for the home side.