A man has been arrested in connection with alleged racist chanting by a group of Chelsea football fans on a train back from the club’s 0-0 draw against Norwich City.
British Transport Police (BTP) said one man was detained on Sunday and remained in police custody in north London.
A spokesman said officers were still looking for other people involved in the alleged incident after the club’s Barclays Premier League match on Saturday.
In a statement made before the arrest, BTP said: “We were made aware of the incident on board the 1600 Norwich to London Liverpool Street service.
“It is alleged that some individuals were involved in racist chanting.
“British Transport Police has contacted the individual concerned who made the allegations and an investigation is ongoing.”
Chelsea have vowed to take action against any fans proved to be involved in racist chanting.
A statement on the club’s website read: “Chelsea Football Club is concerned to hear that a small number of fans travelling back by train from Norwich were alleged to be involved in racist chants and comment.
“We are working to help the relevant authorities identify those responsible and will take the strongest possible action should these allegations prove to be true.
“The club, like the overwhelming majority of our fans, strongly believe that all forms of discrimination are abhorrent and have absolutely no place in society.”
The alleged incident comes just a week before Chelsea face QPR in a potentially explosive FA Cup tie at Loftus Road.
Captain John Terry has been charged with racially abusing QPR defender Anton Ferdinand during the English Premier League game between the two clubs on October 23.
Terry, who denies the allegations, is due to appear at West London Magistrates Court on February 1.
Chelsea were forced to condemn supporters who were clearly heard chanting “Anton Ferdinand, you know what you are” in their 1-1 Champions League Group E draw at Genk’s Cristal Arena on November 1.