Millwall FC and the police are investigating after an alleged homophobic slur stopped play on Saturday.
Match officials reported the incident of alleged homophobic abuse during the first-half of the game against Reading at around 3.30pm.
The club said it carried out standard protocol in making a “tannoy announcement to the crowd as quickly as possible” during the game at The Den.
In a statement, the club said: “The club carried out step one of the advised protocol by making a tannoy announcement to the crowd as quickly as possible.
“A comprehensive investigation into the alleged incident is well underway.
“Millwall Football Club has a zero-tolerance policy against discrimination of any kind. Any individual found guilty of such abuse at The Den is issued with an immediate lifetime ban.”
On Friday morning, police also appealed for information about the “homophobic abuse” which they believe to have involved home fans.
“We take any allegation of abuse very seriously and are investigating this matter,” said DC Phil Dickson.
“If anyone was at last Saturday’s game and witnessed the incident, or has video footage of it, I would urge them to come forward to assist us in our investigation.”
Referee Keith Stroud briefly halted play during the first half after being made aware by an assistant at the side-lines about the alleged homophobic comment.
A tannoy announcement was made by Millwall to both teams’ fans during half-time.
Manager Gary Rowlett has said that he does not know what the comment allegedly was, and has backed the Club to handle the investigation thoroughly.
It comes after Millwall was fined £10,000 for racist chants by some fans during the club’s match against Everton in the FA Cup last year.
Police have asked witnesses or those with video footage to contact them on 020 8246 9386.