UEFA is looking into reports that Croatia fans threw a banana at the pitch and racially abused Italy striker Mario Balotelli at the European Championship.
UEFA said Friday it is seeking more information about the incidents, which reportedly happened during the Italy-Croatia match Thursday in Poznan.
An anti-discrimination group appointed by UEFA to work at Euro 2012 said it has "categorical" accounts from two monitors that around 300 people directed monkey chants at Balotelli, who is black.
"They are both categorical. It was not a boo or something that could be misinterpreted," Piara Powar, of Football Against Racism in Europe (FARE), told The Associated Press.
Balotelli has now been the target of alleged abuse at both Italy matches at Euro 2012.
UEFA is investigating claims by a Spanish fans' group that some Spain followers made monkey chants Balotelli during a Group C match last Sunday in Gdansk. Balotelli started for Italy against Croatia, and was replaced in the second half of the 1-1 draw.
"It was fairly consistent throughout the game," Powar said of the monkey noises. "It was at its most intense as he was substituted and left the field."
UEFA asked FARE to provide monitors, who speak the language of both nations, at each Euro 2012 match, and file reports within 24 hours detailing offensive chants, banners and behaviour.
"Our Italian observer was very shocked by what was heard," Powar said. "Self-policing worked with the Spanish fans and it didn't work with the Croatia fans."
UEFA will also receive details of far-right flags and symbols displayed by some Croatia followers, but not the banana incident in the monitoring reports, Powar said.
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.
UEFA rules make national associations responsible for their fans' behaviour. Punishments range from warnings and a sliding scale of fines to points deductions and even expulsion from Euro 2012.
Also Friday, the Croatia FA was fined C25,000 ($31,500) 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." A Croatia fan was tackled by stewards after trying to reach coach Slaven Bilic following the 3-1 win last Sunday in Poznan.
After Croatia led 2-1, Ireland's kickoff was delayed while smoke from fireworks cleared at one end of the stadium packed with Croatia fans.
Italy's kickoff was also delayed by firework smoke on Thursday after Croatia equalized in the 1-1 draw. A further UEFA charge is likely.
Bilic said Friday it was "unbelievable" to see so many fans in Poznan.
"We were like the home side, it also lifted us and we'd like to thank them for coming because we felt their presence," Bilic said. "Unfortunately, you will always find some individuals that cause the problems with some fireworks or with some whistles."
In a separate case Friday, the Italian FA lodged a complaint with UEFA over Croatia fans whistling when Italy's national anthem was played before the match.