Chelsea and Manchester United have been asked to supply the Football Association with statements relating to the post-match scuffle between players and staff at Stamford Bridge on Saturday.
United have already sent a report to the FA, but there is unlikely to be an early conclusion to the investigation as both clubs are involved in Champions League matches this week.
In the meantime, the FA are continuing to seek out all available footage of the incident which was captured by Chelsea's CCTV cameras.
Chelsea were expecting the FA to request a copy of the film later today but allegations the row had been sparked by racist remarks were being played down by both clubs.
It was alleged that a racist comment aimed at defender Patrice Evra was at the centre of the fight which involved up to 30 people.
But a telephone conversation between chief executives Peter Kenyon, currently in India, and United opposite number David Gill, forced United to distance themselves from the allegations.
Kenyon is believed to have called Gill the moment he learned that United were claiming racist taunts had been the reason for the astonishing scuffle.
United asked Evra for his account of the incident as part of their report to the FA.
The unsavoury fracas involved six of United's players, Chelsea ground staff and several match day stewards. The players could find themselves facing disciplinary action from the FA once they have studied the film.
Evra, Gary Neville, Paul Scholes, John O'Shea, Park Ji-Sung and Gerard Pique were asked to run up and down the pitch instead of across it but tempers flared when Neville insisted on their right to warm-down and a scuffle broke out.
Evra is alleged to have thrown a punch at the groundsman who had asked the players to run in the same direction as lawn mowers being used to trim the playing surface.
There is also CCTV images of United and England centre-half Rio Ferdinand kicking out at a female steward in the tunnel area when he left the pitch at the end of United`s 2-1 defeat.
The steward was left with stud marks on her right shin, although Ferdinand left the United dressing and apologised in person for his action.