Chelsea says ref used 'inappropriate language'

Clattenburg sent off two Chelsea players in the game at Stamford Bridge and allowed a Javier Hernandez's contentious late winning goal that appeared to be offside.

"We have lodged a complaint to the Premier League match delegate with regards to inappropriate language used by the referee and directed at two of our players in two separate incidents in today's match," Chelsea spokesman Steve Atkins said. "The match delegate will pass the complaint to the Football Association."

The Professional Game Match Officials Board, which oversees topflight referees in England, said in a statement that it is "aware of the allegations and they are being treated with the utmost seriousness."

"Mark will cooperate fully and welcomes the opportunity for the facts to be established," the statement added. "No further comment will be made until this matter has been properly investigated."

Premier League referees wear microphones in matches and their audio is usually heard by the other match officials during games. Clattenburg is one of the FIFA candidates to referee at the 2014 World Cup in Brazil.

United climbed back above third-place neighbor Manchester City on goal difference, while Tottenham returned to fourth place with a 2-1 victory at Southampton.