Chelsea have confirmed that they have lodged a formal complaint to the Football Association over "inappropriate language" used by referee Mark Clattenburg to midfielder John Obi Mikel.
The match official is alleged to have called Mikel a "monkey" during the Blues' 3-2 defeat to Manchester United on Sunday.
Chelsea released a statement, which said: "This is a result of a thorough investigation carried out by the club, and led by outside legal counsel, of all information available to us including interviews with a number of players and staff.
"Following Sunday's Premier League game against Manchester United, club board members were quickly made aware, upon entering the home dressing room after the final whistle, that there were allegations of inappropriate language directed at Chelsea FC players by Mr Clattenburg during the game."
The West London club went on to say that they have dropped claims that a second player, believed to be Juan Mata, had also received unsavoury comments from Clattenburg during the match due to insufficient evidence.