The Football Association’s prospects of discovering who was to blame for the skirmish between players and staff of Manchester United and Manchester City on Sunday may be remote after it emerged there are no CCTV cameras in the corridor near the changing rooms at Old Trafford.

The extraordinary bust-up occurred outside the away dressing room during City’s celebration of their 2-1 victory over United. A melee developed which left Mikel Arteta, an assistant coach at City, with blood on his face. Stewards and police were required to break up the opposing sets of players and staff.

The FA has asked for each club’s observations and on Wednesday extended the time allowed from 6pm on that day to the same time on Friday. Both City and United are expected to argue they were the passive party.