Match officials have been interviewed by the Football Association over allegations from Chelsea that referee Mark Clattenburg used "inappropriate language" against John Mikel Obi.
Chelsea accused the referee of using an offensive racial term during the 3-2 defeat by Manchester United in October.
A decision on whether any action will be taken is expected early next week.
The FA is understood to have interviewed Clattenburg, his assistants and fourth official Michael Jones.
The referee denies the allegations and neither assistants Michael McDonough and Simon Long or the fourth official are understood to have heard anything that supports Chelsea's allegations.
All four officials wear microphones and ear pieces that allow them to hear what each other is saying during the game.
Clattenburg, 37, will not officiate a match this weekend for a second successive week.
Chelsea said the complaint was made following a thorough investigation, which they claimed was led by outside legal counsel and used information from interviews with Blues players and staff.
The Metropolitan Police also started an investigation into the allegations after receiving a complaint from a source outside the game.