Chelsea Football Club have condemned an incident, captured in amateur video footage in the Paris metro, that shows fans pushing a black man off a train and chanting "we're racist".
The video was filmed before Chelsea's Champions League match against Paris St Germain at the Parc des Princes stadium in Paris on Tuesday evening.
The men can be heard chanting "we're racist, we're racist, and that's the way we like it".
A Paris police prefecture spokesman said on Wednesday that no immediate complaint had been filed in relation to the video which was posted on the website of The Guardian newspaper.
"We will now assess the video of the (Richelieu-Drouot) incident and, if there is cause, launch an investigation in conjunction with our British colleagues," he added.
The spokesman said police, including about 10 British officers, had been deployed across Paris on Tuesday and prevented several fights from breaking out.
He said they had only just been appraised of the incident in the video, but added that, with the faces clearly visible, it should be easy to identify the men.
Chelsea, whose image was badly tarnished in the 1970s and 1980s when the right-wing National Front regularly recruited on their old terraces at the notorious Shed End of Stamford Bridge, condemned the incident on Wednesday.
"Such behaviour is abhorrent and has no place in football or society," the club said in a statement in response to the reports.
"We will support any criminal action against those involved, and should evidence point to involvement of Chelsea season-ticket holders or members the club will take the strongest possible action against them, including banning orders."
The amateur footage, posted on The Guardian website, shows a black man trying to squeeze onto a busy train at the Richelieu-Drouot metro stop only to be pushed back repeatedly by a group of men.
After stopping him from boarding the train, they start their chants.
Paul Nolan, a British resident of Paris who filmed the video, told BBC Radio Four the Chelsea fans in the metro carriage had seemed "very aggressive" and it was an "ugly scene".