UEFA on Wednesday said that it was bringing fresh disciplinary proceedings against Croatia after "racist banners and symbols" were seen at the country's final group match against defending champions Spain.
The case comes a day after European football's governing body fined the Croatian Football Federation 80,000 euros ($100,000, 64,500 pounds) after its supporters racially abused Italy's Mario Balotelli when the countries met on June 15.
That fine was criticised for being less than the 100,000 euros against Denmark's Nicklas Bendtner for flashing the sponsored waistband of his underpants in a goal celebration in contravention of laws governing unauthorised player advertising.
UEFA's latest statement said that its Control and Disciplinary Body would rule on Sunday on "the setting-off and throwing of fireworks, and the improper conduct of supporters (display of racist banners and symbols)" at Monday's match.
No details were given about the exact nature of the banners or symbols but the statement added: "The disciplinary case also involves the improper conduct of the team (six Croatian players received a yellow card during the match)."
Spain won the game 1-0 to finish top of Group C, setting up a quarter-final meeting with France on Saturday.