Chelsea fans have been accused of singing antisemitic chants during an away match against Hungarian team Vidi in Budapest on Thursday night.
A complaint was lodged with Uefa after the London side's supporters reportedly used an antisemitic term in a song aimed at rival club Tottenham.
In a chant that is familiar to Chelsea regulars, the words "Barcelona, Real Madrid, Tottenham are a bunch of Yids... Yiddos" could be heard from the Groupama Arena away end.
This follows a club and police investigation into alleged racist abuse aimed at Raheem Sterling at Stamford Bridge last weekend.