Mark Clattenburg is understood to have told the FA that John Obi Mikel hurled expletive-laden threats in the refereesβ room after Chelseaβs loss to Manchester United.
Under-fire Clattenburg has chronicled in detail the startling flashpoint that unfolded off the pitch as a climax to the mayhem on it.
The Premier League, who have already seen his version of events, refused to comment on it on Monday night.
Clattenburg has filed an extraordinary incident reportβ.
In it, he is believed to have listed an explosive time-line of events that took place during a confrontation in his designated area that sources claim descended into scenes resembling a pub brawlβ.
Extraordinary incident reports are normally filed when referees believe an incident has taken place that falls outside their jurisdiction on a match-day and into that of the FA.
The Mirror understands the scenes in Clattenburgβs dressing room area took place almost two hours before Chelsea revealed they were reporting the Gosforth official to the Premier League for allegedly using a racial slur towards two Blues players Mikel and Juan Mata on the field of play.
Yet while Clattenburg found himself at the centre of the unprecedented accusations, the latest shocking claims could lead to problems for the European champions.
They would come in addition to the hot water in which they find themselves following the behaviour of supporters who aimed coins and a seat at celebrating United players on Sunday.
It was at around 6.05pm, minutes after the final whistle of Unitedβs win, that Clattenburg and his assistants Simon Long and Michael McDonough were confronted in the officialsβ dressing room by a Chelsea delegation.
The party consisted of chief executive Ron Gourlay, manager Roberto Di Matteo, his assistant Eddie Newton and Mikel.
They had gone into the refereeβs room demanding a reponse from Clattenburg after making the claim that the official had insulted two of their players.
Clattenburg, who had sent off Chelsea players Branislav Ivanovic and Fernando Torres and allowed a United winner scored by an offside player, refused.
Matters quickly became heated, with Mikel seen and heard screaming in the direction of Clattenburg.
Banging and shouting could be heard coming from the refereeβs dressing room.
Seconds later, tunnel security staff rushed into the room to come between the two parties.
They were followed into what is an enclosed area by Chelsea captain John Terry, who watch the game from the stand while continuing his FA suspension for racially abusing QPR’s Anton Ferdinand.
Terry raced from the other end of the tunnel area around 15 yards to join the melee.
The door was then closed, and the shouting and screaming continued for several further minutes.
One source told the Mirror: It was like a fight had started in a pub and all the bouncers were rushing in to deal with it.β
Once the fracas was calmed down, Terry emerged, followed by Gourlay and Newton, Mikel and the security staff.
The door was again closed, leaving Di Matteo alone with the officials.
Several minutes after that, the Italian came out drenched in sweatβ, before regaining his composure to go and speak to the media.
Di Matteo later confirmed at his press conference that he had been to see the referee.
But he did not reveal the incendiary events that had also taken place in Clattenburg’s room.
An hour after Di Matteo had concluded his media duties, Chelsea confirmed they were lodging a complaint with Premier League match delegate Nick Cusack, relating to inappropriate languageβ used by Clattenburg towards two players.
Although the club refused to elaborate on the nature of what was said, they were understood to be claiming Clattenburg had used language that could be interpreted as racially offensive.
At least three Chelsea players are said to be ready to give statements to the FAβs disciplinary committee.
The FA, however, will speak to, and where appropriate take written statements from, ALL relevant parties connected with Sundayβs events – players, officials and stadium staff.
The Premier League received Clattenburgβs report on Monday morning.
It was in turn forwarded to the Football Association who announced within hours that they were launching an investigation.
Chelsea have instructed their players not to discuss the matter publicly as the process takes its course.
They could yet, however, find themselves in the dock as well.