West Ham have said the club is "appalled" after footage of fans singing an anti-Semitic song towards a Jewish man on a plane circulated online on Thursday.
A video shows a man walking down the aisle to take his seat on the plane, with a group of supporters signing an offensive chant. West Ham played in Genk, Belgium, on Thursday night and drew 2-2 in the Europa League.
A West Ham spokesperson said: "West Ham United is appalled by the contents of the video circulating on social media and condemn the behaviour of the individuals involved. The club is liaising with the airline and relevant authorities to identify the individuals.
"We continue to be unequivocal in our stance -- we have a zero-tolerance approach to any form of discrimination. Any individuals identified will be issued with an indefinite ban from the club. Equality, diversity and inclusion are at the heart of the football club and we do not welcome any individuals who do not share those values."
Said Benrahma scored twice in the Hammers' 2-2 draw in what was David Moyes' 1,000th match in management. The result meant Moyes' side qualified for the Europa League knockout stages.
Speaking ahead of Sunday's Premier League clash against Liverpool, Moyes told a news conference: "We are a diverse football club. There's no room for discrimination anywhere.
"I'm really disappointed to hear about it. I'm sure it's only individuals and not a big section of supporters. I'm just sorry to hear about it. I want this football club to be recognised for having a really good football team. I want this football club to be recognised as being a great club in London and well respected.
"We have incredible supporters who follow us home and away but I don't want any labels connected to this whatsoever -- discrimination or racism, none at all. We don't want to be associated with supporters like this. I want us to fully move on from this."