Chelsea are reminding fans that racism of any kind is "unacceptable" and "unwelcome" following allegations of anti-Semitic chanting during Sunday's game at Crystal Palace.
It is alleged the offensive singing started when Palace forward and former Tottenham player Andros Townsend touched the ball during Chelsea's 1-0 win.
There have been a number of incidents in recent weeks that prompted Chelsea chairman Bruce Buck to write an open letter to supporters condemning the actions of a "few mindless individuals".
Buck said: "A deeply unpleasant but vocal minority which refuses to join us in the 21st century has shamed the great majority of our decent, well-behaved fans."
The Metropolitan Police investigated claims that Manchester City forward Raheem Sterling was subject to racist abuse at Stamford Bridge.
Chelsea ended up suspending four fans from matches. They also spoke out against anti-Semitic chants during the club's Europa League tie with Mol Vidi.