UEFA moved to stamp out racism at the European Championship for the first time on Saturday after opening disciplinary proceedings against Croatia over the alleged abuse of Mario Balotelli.
European football's governing body announced they were taking action against the Croatian Football Federation (HNS) over racist chanting by their fans in the country's 1-1 Group C draw against Italy on Thursday.
Press Association Sport understands claims a banana was thrown on to the field in Poznan were taken into account, as was the displaying of racist banners at the Municipal Stadium.
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 on Friday their observers heard between 300 and 500 Croatia fans chanting monkey noises at Italy striker Balotelli in Thursday's match.
That followed reports a photographer witnessed a steward retrieving a banana from the pitch as well as hearing the same chants.
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.
It is understood UEFA are still probing allegations the Manchester City striker, 21, was subjected to monkey chants in Italy's opening match against Spain on Sunday.
The Italian Football Federation decided against making an official complaint against that or Thursday's alleged repeat episode because none of their delegation had witnessed it at the time.
As well as incidents surrounding Balotelli, UEFA have been looking into claims Czech Republic defender Theodor Gebre Selassie was subjected to monkey chants during his side's Group A opener against Russia last Friday.
Holland players claimed they heard racist chanting during an open training session in Krakow last Wednesday before the tournament even began.
Saturday's announcement of proceedings against Croatia followed a 25,000-euro (£20,298) fine on Friday after their fans set off and threw fireworks and missiles, and a supporter invaded the pitch, during Sunday's win over Republic of Ireland.
The HNS were fined £14,920 by FIFA just under four years ago after then England striker Emile Heskey was subjected to monkey chants in a World Cup qualifier in Zagreb.
Croatia were also given a small fine during Euro 2008 for racist abuse from their fans during their game against Turkey.
The HNS condemned the "deviant" fans on Saturday who had shamed their country but urged UEFA to spare them further sanctions.
They said in a statement: "[The] Croatian Football Federation distances itself from all deviant behaviour of the part of the fans during the final tournament of UEFA Euro 2012 and strongly condemns it.
"[The] Croatian Football Federation, its national team players and members of the technical staff support all UEFA activities aimed at identifying individuals whose behaviour damages the reputation of the competition, no matter which country they come from.
"[The] Croatian Football Federation appeals to UEFA not to punish the Croatian national team, which is for a number of years at the top of world football because of its performances and behaviour, both on and off the field of play, and not to associate it with the part of the fans who actually are not supporters, but hooligans which should be isolated from all sports events."
This week saw Russia hit with a suspended six-point deduction for their Euro 2016 campaign over the behaviour of their fans at Euro 2012, which included the display of extremist banners.