UEFA says it will investigate allegations racist incidents occurred during Chelsea's Europa League tie at Vidi in Hungary last week.
Anti-semitic chants were reported to have been heard during the 2-2 draw in Budapest, and supporters were also pictured in the city with a flag featuring a Nazi symbol, although authorities believe the flag did not make it inside the Groupama Arena.
The incident occurred five days after the club and Metropolitan Police launched other investigations into allegations that Manchester City forward Raheem Sterling was racially abused in a Premier League match at Stamford Bridge.