"UEFA has today opened disciplinary proceedings against the Croatian Football Federation (HNS) for the setting-off and throwing of fireworks, and the improper conduct of supporters (display of racist banners and symbols) at the UEFA Euro 2012 Group C match against Spain in Gdansk on Monday," the governing body said in a statement.
The disciplinary case, UEFA said, also involves the "improper conduct" of the Croatian team after six of their players were booked in the 1-0 defeat which condemned them to a group stage exit.
UEFA will deal with the latest case on Sunday.
Croatia were fined 80,000 euros after fans directed racist abuse at Italy striker Mario Balotelli and set off fireworks in Croatia's second group game in Poznan on June 14.
The HNS had already been fined 25,000 euros by UEFA for "spectator incidents" during their opening match, also in Poznan.
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