Paris, France: UEFA has launched an investigation into alleged racist chants during Chelsea's Europa League tie at Vidi, the governing body announced on Tuesday.
Minutes into the Europa League match in Budapest on December 13, which ended 2-2, a vocal minority of Chelsea fans were heard allegedly singing a derogatory chant about Tottenham Hotspur supporters, featuring anti-Semitic language.
Chelsea condemned the chanting and promised to take the strongest possible action against any supporters found to be guilty of singing racist songs.
The incident in Hungary came a matter of days after four fans were suspended for abusing Manchester City's Raheem Sterling.
The England forward later issued a statement accusing the British media of fuelling racism in the way it reports certain stories about black players.
Chelsea banned four supporters pending an internal inquiry.
The results of UEFA's investigation will be published by the middle of January.