Uefa has opened disciplinary proceedings into alleged racist chanting by Chelsea fans in the Europa League game with MOL Vidi.
A vocal minority chanted offensive songs about Tottenham fans in the 2-2 draw in Hungary on 13 December.
Chelsea said fans who sang an anti-Semitic chant during the game had "shamed the club".
Uefa's control, ethics and disciplinary body will rule on the case at its next meeting on 28 February.
The events in Hungary came five days after the alleged racist abuse of Manchester City's Raheem Sterling by some Chelsea supporters during a Premier League game at Stamford Bridge. Four fans were suspended by the club.
Chelsea chairman Bruce Buck greeted Chelsea supporters at the turnstiles before a Premier League win at Brighton on 16 December and wrote an open letter condemning the actions of "a few mindless individuals".
In October, Buck told the Sun newspaper Chelsea may require fans found guilty of anti-Semitic abuse to visit the site of Nazi concentration camp Auschwitz rather than ban them.
"If you just ban people, you will never change their behaviour," he said.
The club's Say No to Anti-Semitism scheme, which began in January, provides one-to-one education courses.
A group of 150 Chelsea club staff, stewards and supporters visited Auschwitz in June to learn about the deaths of more than a million people there between 1940 and 1945.