John Terry, the Chelsea and England captain, is being investigated by police over allegations of racist abuse against the Rangers player and some supporters chanted 'Anton Ferdinand you know what you are' in Belgium on Tuesday night.
"It [the chanting] was wholly inappropriate and we don't condone it," a spokesman for the London club told Reuters on Wednesday.
Chelsea went 1-0 up with a 26th-minute goal from midfielder Ramires and then missed a first-half penalty through defender David Luiz.
Genk earned a share of the spoils after Jelle Vossen equalised from close range in the 61st minute.
Chelsea have a two-point lead over Bayer Leverkusen at the top of Group E.
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