West Ham are determined to find those responsible for abuse directed at Liverpool forward Mohamed Salah – and to ban them from the London Stadium.
The Egypt international was filmed on a mobile phone from a section of home supporters as he was taking a corner during Monday night's Premier League match against the Irons.
The video clip contains audible expletives directed at the Liverpool player, including comments against his Muslim religion.
The user who posted the video on Twitter said: "I was disgusted by what I was hearing. People like this deserve no place in our society let alone football matches. #kickracismout"
Having been tagged in the social message post, the Football Association were made aware of the video, which was shared with West Ham for investigation as a matter of urgency, Press Association Sport understands.
West Ham are taking immediate action to identify the individual, or individuals concerned, and intend to hand their details over to the police so they can be banned from attending football matches.
The Metropolitan Police are also reviewing the footage.
A West Ham spokesperson said: "At West Ham United, we have a zero tolerance policy to any form of violent or abusive behaviour. We are an inclusive football club.
"Regardless of age, race, religion or belief, marriage or civil partnership, pregnancy or maternity, sex, sexual orientation, gender reassignment or disability, everyone is warmly welcomed at London Stadium.
"Anyone identified committing an offence will have their details passed to the police and will face a lifetime ban from London Stadium. There is no place for this kind of behaviour at our stadium."
Premier League leaders Liverpool drew the match 1-1, which dented their hopes of putting more pressure on rivals Manchester City in the race for the title.
The Metropolitan Police said officers are in the process of reviewing the footage. No arrests have been made and enquiries continue.
"Anyone who witnesses inappropriate behaviour during a match is urged to bring it to the attention of a steward or police officer," a statement from the Metropolitan Police added.
Kick It Out, football's equality and inclusion organisation, offered their support to the investigations.
"We are dismayed to see yet another high-profile incident of discrimination in English football – this time a video of disgraceful anti-Muslim abuse aimed at Liverpool's Mohamed Salah by a West Ham United supporter," the anti-discrimination campaign group said in a statement to Press Association Sport.
"We have informed the club, the FA and the UK Football Policing Unit and have offered our support to the investigation, which is already under way.
"We are pleased that West Ham officials have expressed their determination to identify the supporter and take firm action – this type of behaviour is simply unacceptable and must be challenged swiftly and decisively."