Thierry Henry was struck by a missile during Arsenal's FA Cup quarter-final clash with Chelsea at Highbury.
The Football Association may launch an investigation into the incident once they have received reports from the match officials.
The object was hurled at Henry from the Clock End, which was full of Chelsea fans, after the Arsenal striker had struck the post and he walked off the pitch to hand it to the fourth official.
It was later confirmed that the missile had struck the Frenchman, although it did not contribute to the injury which could keep him out of Arsenal's Champions League tie against Roma on Tuesday night.
Boss Arsene Wenger said: "I don't know what the object was, frankly. I didn't ask the fourth official. Thierry didn't say to me whether it had hit him, maybe he said that to the fourth official."