Chelsea will ban any supporters found to have used anti-Semitic language or behaviour which "shames" the club during the defeat at Watford on Monday.
Chelsea were beaten 4-1 by Watford at Vicarage Road in the Premier League.
A report on a Jewish website said one fan was left "disgusted" by chanting from fellow Blues supporters, reporting the incident to stewards at the ground.
"Anti-Semitism has no place in our club, football or wider society," said a Chelsea statement.
The club have launched an investigation in co-operation with Watford and the police.
The statement added: "Anyone found guilty of anti-Semitic language or behaviour will face action from the club, including bans, and will be asked to attend equality education courses.
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"We welcome the fact that Chelsea fans have reported this behaviour, which shames our club."
The club last week launched a 'Say No to Anti-Semitism' campaign as part of their own inclusion work through the Building Bridges initiative.
Source:BBC