Croatia are facing a possible stiff penalty after UEFA said on Saturday it was taking action over racist chanting against Italy's Mario Balotelli, with tough sanctions already meted out to deal with crowd trouble.
UEFA's Control and Disciplinary Body is to announce its decision on Tuesday over what the organisation said was "the setting-off and throwing of fireworks, and the improper conduct of supporters (racist chants, racist symbols)" at Thursday's match.
The Group C match in Poznan, western Poland, finished 1-1.
The sanction imposed on the Croatian football federation will be eyed closely given UEFA president Michel Platini's repeated assertion that there was "zero tolerance" for racism - and football-related violence - in the European game.
The same committee this week imposed the threat of a six-point reduction on Russia's next European championship qualifying campaign, after missiles and fireworks were thrown at their opening Group A match against the Czech Republic on June 8.
Four stewards also required hospital treatment when they were set upon after the game, which Russia won 4-1.
The latest disciplinary proceedings are the first case for racism in the competition, which started with fears of racist violence at football grounds in host countries Poland and Ukraine and which have refused to go away.
UEFA is already probing separate claims that a section of Spanish fans racially abused Balotelli, who is of Ghanaian origin, and that Russian supporters taunted the Czech Republic's Theodor Gebre Selassie, who is of Ethiopian descent. Dutch players also alleged they heard monkey noises during a public training session in Krakow, southern Poland, although no official complaint was made.
The latest allegations involving Balotelli, who is one of the best known footballers in Europe, emerged after an AFP photographer and a racism monitoring body said they heard racist chanting at the Italy-Croatia match. The photographer, who was positioned in front of the majority of Croatia fans during the match, also saw a steward pick up a banana from the pitch.
Balotelli, 21, has previously said that he would walk off the pitch if he were racially abused during a match.
The executive director of the UEFA-backed Football Against Racism in Europe (FARE), Piara Powar said between 300 and 500 Croatia fans were involved in racist chanting.
"That is a big number. It was fairly intermittent but progressive throughout the game. It intensified when Balotelli was substituted," said Powar.
Croatia's management refused to comment on the allegations at their training camp base south of the Polish capital, Warsaw, on Saturday, where they were preparing for their match on Monday against European and world champions Spain.
Team spokesman Davor Gavran said a statement was being prepared and told reporters: "It is not a question for the players today before a crucial game."
The Italian football federation also refused to comment, although they said on Friday that no player, including Balotelli, had mentioned either being abused or the throwing of a banana.
Coach Cesare Prandelli has strongly rejected the previous claims of abuse against the player during the Spain game.
Croatia has already been in the dock for the behaviour of its fans at Euro 2012. On Friday UEFA fined the country's football federation $31,400 after fans lit flares and let off smoke bombs to celebrate goals in their opening match.
Missiles were also thrown and a spectator got on to the pitch in Croatia's 3-1 win against the Republic of Ireland, which was also held in Poznan.