Uefa is looking into reports that a banana was thrown on to the pitch in a racist attack by Croatia fans during the Euro 2012 match against Italy.
European football's ruling body said it is seeking more information about the incident, which reportedly happened on Thursday in Poznan, Poland.
Uefa said it had not opened a disciplinary case against the Croatia football association. Italian officials had also not formally complained.
Both Italy matches at Euro 2012 have now been the subject of alleged racist abuse by its opponent's fans.
Spain's fans have been self-policing, with Uefa investigating claims by one group that some fellow supporters made monkey chants at Italy forward Mario Balotelli , who is black, during a Group C match last Sunday in Gdansk.
Before the tournament, Balotelli said in an interview that he would want to "kill" anyone who threw a banana at him. He also threatened to walk off the pitch if he was racially abused.
The Croatian FA has already been fined �?�25,000 (£20,170) for its fans' behaviour at an earlier match against Ireland.
Uefa said the sanction was imposed for "the setting off and throwing of fireworks and missiles, and a pitch invasion by a supporter".
In a separate case, the Italian FA has lodged a complaint with Uefa over Croatia fans whistling when Italy's national anthem was played before the match.
Meanwhile, Uefa has charged Denmark forward Nicklas Bendtner with improper conduct for revealing a brand name on his underpants while celebrating a goal.
The striker lifted his shirt and lowered his shorts slightly, revealing the name of betting firm Paddy Power across the top of his underpants, after scoring his second goal in the match on Wednesday. Denmark eventually lost 3-2 against Portugal.
The stunt did not go down well with rival British gambling company Ladbrokes, one of the Danish FA's official sponsors.
"We have an exclusive deal... and this is of course a breach of it," said Lars Berendt, a Danish FA spokesman.
"And it's also a breach of Uefa's commercial rules, rules against exposing personal messages."
Bendtner is suspected of breaking law 4 of football regarding players' kit and equipment, Uefa said in a statement.
The football body's disciplinary panel will deal with the case on Monday.
Uefa tournament rules for Euro 2012 bar any sponsor advertising on players' kit.
Bendtner got a dressing down from the Danish Football Association on Thursday for flouting team policy.
Danish team officials have told Bendtner he must abide by rules with his match-day underwear when Denmark plays Germany in the final round of Group B matches on Sunday in Lviv, Ukraine.
On Friday, Bendtner flashed his fresh, regulation-friendly black underpants at training in an apparent sign of his eagerness to co-operate.