West Ham fans have been accused of singing an anti-Semitic chant in a Jewish area of London ahead of their side's clash with Tottenham Hotspur at White Hart Lane.
A video clip emerged on Twitter showing alleged Hammers fans on a tube train going through Stamford Hill chanting "I've got foreskin, how about you? F*****g Jew."
Stamford Hill is home to one of the largest Orthodox Jewish communities in Europe and Tottenham have a long-standing connection to the Jewish community.
WARNING: Video contains offensive language
Spurs condemned the chants in a statement: "Anti-Semitism in any form is wholly unacceptable and we support all efforts to kick it out of the game.
"We hope that those individuals responsible for this vile behaviour are identified and dealt with in the strongest way possible."
West Ham has emailed fans reminding them of their duty as club ambassadors and said it had a "zero-tolerance policy" towards such chants and could ban those responsible.
Anti-racism group Kick It Out said it had received reports of the incident and notified police.
British Transport Police is investigating the alleged racism, saying it is taking it "very seriously".
West Ham and Tottenham fought out a 2-2 draw at White Hart Lane on Sunday (22 February) after the Hammers had taken a 2-0 lead.
However, an injury time equaliser by Harry Kane secured the north London club a point at the death.
The incident on the London Underground follows a week when the light has been shone on racism in football.
Images of three Chelsea fans were released at the weekend who are wanted in connection with the pushing of a black man from a Paris Metro to chants of "we're racist, we're racist and that's the way we like it."