The Football Association (FA) is to investigate allegations of racist chanting from a section of Millwall fans during Saturday's FA Cup win over Everton.
Footage on social media appeared to show several supporters taunt away fans using a derogatory term about the Pakistani community during Millwall's dramatic 3-2 win at The Den.
The FA is now planning to look into the matter.
A spokesperson said: "The FA can confirm that we are aware of a video posted on social media after the FA Cup match between Millwall and Everton.
"Discriminatory behaviour and chanting has no place in football and we will be investigating the matter."
Millwall also condemned the "abhorrent" chants and vowed to issue life bans for anyone found to be involved.
A Millwall statement read: "Millwall Football Club is aware of, and extremely disappointed by, a video circulating online displaying alleged racist chanting during Saturday's victory over Everton.
"The club will, as is commonplace following such incidents, work with all relevant authorities during investigations into the matter and look to identify individuals involved. Anyone identified and guilty of such abuse will be banned from The Den for life.
"The club would like to place on record its gratitude to, and pride in, the vast majority of its supporters who gave their team outstanding backing throughout the match and who deserve to enjoy a memorable victory.
"They should be able to do so without being tarnished by behaviour they would find abhorrent.
"Millwall Football Club has a long and proud record of anti-discrimination work and on top of this investigation will continue to work tirelessly, alongside the authorities, to eradicate all forms from the game."
Before the match, a fracas between rival fans led to one man being left with a slash wound to his face.
Millwall's victory came via Murray Wallace's late strike, which followed a controversial leveller from Jake Cooper, who had seemingly directed the ball in with his arm.