Chelsea have lodged a formal complaint with the Football Association over "inappropriate language" they claim Mark Clattenburg used against John Obi Mikel in their acrimonious defeat to Manchester United.
But the Blues decided not to pursue an allegation referee Clattenburg also used words understood to have been interpreted as racist towards Juan Mata during Sunday's game following an internal investigation carried out by external legal counsel.
Press Association Sport understands Chelsea submitted signed witness statements from a number of players and staff to the FA, who had already begun their own probe into the matter.
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