Luis Suárez has been accused of racially abusing Patrice Evra in the north-west derby between Liverpool and Manchester United at Anfield.
The players were involved in a running dispute early in the second half, when Evra was booked for what appeared to be dissent over referee Andre Marriner's interpretation of their feud.
Evra made his accusation via the French television station Canal Plus, to whom he said: "There are cameras, you can see him. He says a certain word to me at least 10 times."
He added: "I was very upset. In 2011 you can't say things like this. He knows what he said, the ref knows it, it will come out. I won't repeat what he said, but it was a racist word, and he said it more than 10 times. He tried to wind me up. I won't make a huge deal out of it, but it's very upsetting and disappointing."
A statement from the Football Association confirmed they were investigating the incident. "The FA have this evening been made aware of an incident that is alleged to have occurred during the Liverpool versus Manchester United fixture at Anfield today," the statement said. "Referee Andre Marriner was made aware of an allegation at the end of the fixture and reported this to the FA. The FA will now begin making inquiries into the matter."
A Liverpool spokesman said: "The first we knew about these allegations was 20 minutes after the final whistle when the manager was asked to go into the referee's office and told about them. The first thing we did, as you would expect, is ask the player and he has categorically denied using any language of that nature."
Evra has been the subject of alleged racial taunting before, and complained about it, but Suárez has seldom been out of the headlines since the World Cup in South Africa last year, when he famously handled on the line to prevent a Ghana winning goal in the quarter-final, was sent off, and then was caught laughing about it as his Uruguay side won on penalties to reach the semi-final.
Back playing for Ajax in Holland the following season, Suárez picked up a seven-match ban after being found guilty of biting the PSV Eindhoven midfielder Otman Bakkal. The Dutch Federation quite reasonably deemed that a violent act, and though Suárez's career in England has so far been free of acts of cannibalism, his undoubted skills have not been completely unblemished.
The red card that Everton's Jack Rodwell received in last month's Merseyside derby, widely disputed and subsequently rescinded, came about largely because of Suárez's theatrical reaction to what was little more than a tap on the foot by Rodwell's trailing knee.
The Anfield game ended amicably enough – Javier Hernández salvaged a 1-1 draw for United by equalising after Liverpool's captain, Steven Gerrard, scored from a free-kick – though for several minutes Evra and Suárez were clearly in each other's faces, with the French defender in particular appearing to be unhappy.
According to sources at the game Ferguson accompanied Evra to speak to Phil Dowd, the fourth official, in his dressing room, and Dowd was then seen to visit the teams' dressing rooms.
