Police investigate claims against Clattenburg
Police have launched a formal investigation into allegations Mark Clattenburg used "inappropriate language" towards John Obi Mikel.
The Metropolitan Police confirmed they had acted on what they described as a "complaint" made by the Society of Black Lawyers after the Blues accused referee Clattenburg of using comments that are understood to have been interpreted as racist remarks.
Press Association Sport understands the 37-year-old completely rejects the allegations against him, which are also the subject of a Football Association investigation.
A police statement read: "An investigation has been launched into alleged comments made during a football match between Chelsea FC and Manchester United FC at Stamford Bridge on 28 October 2012.
"This follows on from a complaint received by the Metropolitan Police Service on 29 October. Officers from Hammersmith & Fulham borough are in liaison with Chelsea Football Club and the Football Association.
"At this time, the MPS has not received any complaint from either Chelsea Football Club, or the Football Association. We continue to work in partnership with Chelsea Football Club and the Football Association in order to consider any allegation that is made in relation to the reported events."