Mario Balotelli was racially abused during Italy's 1-1 Euro 2012 Group C with Croatia at the Municipal Stadium in Poznan, Poland, an AFP photographer at the game said.
The photographer was situated in the corner where the majority of Croatian fans were sitting during Thursday's match and said he heard monkey noises being directed at Balotelli.
At one point he also saw a steward picking up a banana that had been thrown onto the pitch.
There was no immediate comment from UEFA, who said only that they were awaiting the referee's report from the match.
On Tuesday UEFA said it was invesigating claims Balotelli, who is of Ghanaian origin, was racially abused during Italy's 1-1 draw with Spain in Gdansk on Sunday.
Italy coach Cesare Prandelli, though, had strongly rejected the claims that Balotelli was abused against Spain. "That's absolutely untrue," he said at a press conference.