Chelsea players including Ashley Cole have been interviewed by the Football Association as part of its investigation into the club's allegation that referee Mark Clattenburg used "inappropriate language" towards John Obi Mikel.
Chelsea made an official complaint against the 37-year-old official following their match against Manchester United at Stamford Bridge on October 28.
The Blues, who lost 3-2 in controversial fashion, alleged that Clattenburg had spoken inappropriately to Mikel, with some Blues players understood to have said that a racist term was used.
Clattenburg has strenuously denied the allegation. With no FA verdict expected until later this week, he will not officiate for a fourth successive weekend - a situation he has welcomed, saying he does not want to take charge of any matches while the case is ongoing.
The FA has spoken to Clattenburg, Mikel, the assistant referees for the United game, Michael McDonough and Simon Long, and fourth official Michael Jones.
An independent QC is studying all the evidence in close detail before recommending a decision. The FA is approaching the case with caution because it arose so soon after Blues skipper John Terry was handed a four-match ban for racially abusing Anton Ferdinand in a game against QPR last October.
A police investigation into the allegation against Clattenburg was stopped due to a lack of evidence earlier this month, with Scotland Yard saying the failure of a victim to come forward had led to the decision being taken.
Chelsea chairman Bruce Buck defended the club's move to report Clattenburg to the FA, claiming they would have been "crucified" had they not taken action.
Buck said he felt the reaction to Chelsea's decision to report the official had been "unfair" amid accusations of hypocrisy, because of the club's decision to stand by Terry, and bitterness after the dramatic United defeat.