Manchester United's submission to the Football Association is expected to include the claim that Patrice Evra was allegedly called “an immigrant” during the mêlée with Chelsea groundstaff at Stamford Bridge, The Times understands.

Chelsea and their employees have strenuously denied that any such remark was made and Evra sought at the weekend to distance himself from suggestions that he was racially abused. But the FA has demanded written statements from both clubs and at least one member of the United staff who were present during the confrontation will claim that Evra was called a “f***ing immigrant” amid the fracas after their Barclays Premiership defeat on Saturday.

As well as Evra, Paul Scholes, Gerard Piqué, Gary Neville, John O'Shea and a fitness coach were close by as they conducted a warm-down.

The Times can also reveal that the brawl was witnessed by Fabio Capello, the England manager, and Franco Baldini, his assistant. Baldini was outside a corporate box using his phone when the trouble started and alerted Capello. It raises the extraordinary possibility of Capello and Baldini being called as witnesses in the inquiry by their employers. Capello later referred to the need for players to show respect in a speech to the Professional Footballers' Association on Sunday evening.

Chelsea have promised to sack any of their staff if they are found to have racially abused Evra. The groundsmen are said to have strongly denied any such behaviour in extensive interviews over the weekend. United had originally suggested that they would be happy for the matter to be dropped, but they are committed to providing the FA with evidence from their players and coaching staff. Maurice Watkins, the club's solicitor, will sit down with the witnesses this week and take their statements.

Having examined CCTV footage yesterday, the governing body wrote to both clubs, giving them a week to provide submissions. The FA will have to decide if there is a case to answer in what has become a fractious row between the clubs over who said what. Chelsea are furious at United for altering their stance several times over the weekend. The title rivals were due to put out a joint statement on Sunday evening, but United withdrew over the wording.

The FA has given both clubs until next week so that they can concentrate on the second legs of their Champions League semi-finals. United face Barcelona this evening, with Nemanja Vidic expected to be ruled out and Wayne Rooney a doubt. Chelsea host Liverpool tomorrow.

Sir Alex Ferguson, the United manager, was eager to steer clear of the controversy at Old Trafford yesterday, but at the third time of asking he responded that he had no concerns about his players' conduct. “We are filing a report which will be sent to the FA,” he said. “We hope the FA investigate it.”

Of more immediate concern for Ferguson is whether Rooney and Vidic will be fit to face Barcelona, having missed training yesterday with hip and facial injuries respectively. Rooney was said last night to be in severe pain and worried about his chances. Ferguson suggested that both players would recover in time, but Rooney may require a painkilling injection if he is to start the match.

Irrespective of the incident at Stamford Bridge, Ferguson issued a resounding vote of confidence in his squad. “I think the first thing is that I trust the players,” he said. “I'm happy for them to represent Manchester United and I think I'm a lucky manager to have such good players. Character-wise they're fantastic. I'm proud to have these players representing me and this club against Barcelona.”