UEFA has opened disciplinary proceedings against the Croatian Football Federation for racist chanting and racist banners in the crowd during Thursday's 1-1 draw with Italy.
On Friday, UEFA confirmed it was 'looking into' claims that a banana was thrown on to the pitch during the Group C encounter in Poznan.
A photographer was reported to have witnessed a steward retrieving a banana during the game as well as hearing monkey chants directed at Italy striker Mario Balotelli.
It was unclear whether the proceedings announced on Saturday were also intended to deal with the claims regarding the banana or if that would be handled separately.
UEFA said in a statement: "UEFA has opened disciplinary proceedings against the Croatian Football Federation (HNS) for the setting off and throwing of fireworks, and the improper conduct of supporters (racist chants, racist symbols) at the UEFA Euro 2012 Group C match against Italy in Poznan on Thursday.
"The UEFA Control and Disciplinary Body will deal with the case on 19 June."
UEFA acted after the FARE (Football Against Racism in Europe) network announced their observers heard between 300 and 500 Croatia fans chanting monkey noises at Italy striker Balotelli in Thursday's match.
If Thursday's purported banana-throwing incident is also shown to be intended as an insult towards Balotelli, the fallout would be potentially the biggest yet at a tournament that has been dogged by allegations of racist abuse.
Balotelli said before Euro 2012 that he would "kill" anyone who threw a banana at him in the street and threatened to walk off the pitch if racially abused.
UEFA had been probing allegations the Manchester City striker was subjected to monkey chants in Italy's opening match against Spain on Sunday.
It was unclear whether it is still looking into that.