Chelsea have been charged by the Football Association after discriminatory chanting was reported during their Premier League game away at Fulham in August.
Following the team's 3-2 win over their west London rivals on the season's opening weekend, the club issued a statement to their fans warning them against "sectarian chanting."
Victory at Craven Cottage came courtesy of goals from João Pedro, Morgan Rogers and Cole Palmer but the club have now been charged with failing to ensure the behaviour of their supporters.
An FA statement read: "Chelsea FC has been charged with breaching FA Rule E21 during the ninth minute of its Premier League fixture against Fulham FC on 24 August.
"It's alleged that the club failed to ensure its spectators and/or supporters did not behave in an improper, offensive, abusive or insulting way. It's further alleged that this behaviour was discriminatory in that it included a reference, whether express or implied, to religion or belief."
The day after the match, Chelsea issued a statement to fans who had been in attendance, which read: "The passion and backing from our fans are vital in achieving a successful season, and we encourage you to continue your vocal support for the team.
"Following the fixture, we have received multiple reports of sectarian chanting from a small portion of those in attendance at the match.
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"We would like to strongly remind all supporters that the club does not condone any chants which discriminate against a protected characteristic. Any supporter found guilty of this will face the strongest possible action, which could include indefinite suspension from attending all Chelsea matches and ejection from the stadium.
"Following previous club fines and charges for chants of this nature, and to ensure that we create a welcoming matchday experience for all, we ask supporters to take collective responsibility and remain vigilant in helping us tackle discriminatory chanting."