UEFA stepped up investigations on Tuesday into alleged racial abuse directed at Italy forward Mario Balotelli and Czech Republic defender Theodor Gebre Selassie.
UEFA said it received new reports "regarding the two cases of alleged racist chanting" at the European Championship.
"UEFA is now conducting further investigations," UEFA spokesman Rob Faulkner said. "There are however, no disciplinary proceedings opened at this moment in time."
UEFA pledged zero tolerance of racism at Euro 2012, but has stressed it needs clear evidence before prosecuting cases through its judicial bodies.
A Spanish fans' group said Monday that "about 200 supporters" made monkey chants at Balotelli during the Spain-Italy match on Sunday in Gdansk, Poland.
Faulkner said UEFA will also seek evidence from Czech team officials about chants directed by Russian fans at Gebre Selassie in Wroclaw last Friday.
Gebre Selassie told The Associated Press that he was abused, but declined to file a complaint.
"It was nothing extreme. I've experienced much worse," said the 25-year-old Czech-born player, whose father is Ethiopian.
Gebre Selassie was expected to play on Tuesday against Greece in Wroclaw. UEFA inquiries are expected to resume on Wednesday.
UEFA rules make national federations responsible for their fans' behavior. A first offense would probably receive just a financial penalty, though further punishments could include deducting group points from teams and ultimately expelling them from Euro 2012.
Italian officials also declined to make an issue of reports that abuse was targeted at Balotelli.
Still, a Spanish group affiliated to the Football Supporters Europe network published a statement explaining that fans attempted to police the problem within their own ranks.
"At some point during the match then, about 200 supporters started monkey chants when the Italian player Mario Balotelli touched the ball," Spain fans' spokesman Thomas Herzog said.
"We're glad to report that the majority of the Spanish supporters reacted in a very positive way, because many of them tried to intervene very quickly and stop the fans in question from singing. We are clearly angry about this small section of Spanish supporters showing this kind of racist behavior."
Balotelli, who was born in Italy to Ghanaian parents, said before Euro 2012 that he would walk off the pitch in protest if he heard racial abuse.
The racism debate was fueled last month by a British television program which broadcast pictures of racism and violence at recent club matches in co-host nations Poland and Ukraine.
The first incident at Euro 2012 happened two days before the opening match when monkey chants were targeted at Netherlands players during a public training session attended by 25,000 people last Wednesday in Krakow, Poland.
UEFA was unable to get footage or recorded evidence to prove the Dutch players' allegations.
On Monday, UEFA said it had written to Poland's sports minister and mayors in cities hosting matches and training camps urging them to police training sessions more intensively and prosecute offenders.
After four matches played in Ukraine, UEFA said Tuesday that no incidents have been reported.
"Nobody made any comments to us regarding racism — no players, no teams, no fans," tournament director Markiyan Lubkivskyi said at a briefing in Kiev.
Associated Press writer Eric Willemsen in Kiev, Ukraine, contributed to this report.
Graham Dunbar can be reached at http://twitter.com/gdunbarap