The Football Association will reportedly have no CCTV footage of the melee which followed Sunday's Manchester derby at Old Trafford.
Players and staff from Manchester United and Manchester City were involved in a furious bust-up in the wake of their derby, which City won 2-1 to move 11 points clear at the top of the table.
United striker Romelu Lukaku is alleged to have thrown a bottle which caused a facial wound to City coach Mikel Arteta, while Jose Mourinho is understood to have had milk and water thrown at him during a heated row with Ederson.
The FA has asked for each club's account of the incident, and today extended the deadline for them to submit those until Friday.
However, the governing body's hopes of getting to the bottom of the ruckus could be scuppered by the lack of CCTV footage available after it emerged that there are no cameras near the changing rooms in the Old Trafford tunnel.
Both clubs are expected to argue that the other was the aggressor during the row, which is likely to confuse matters further for the FA when it comes to dishing out any potential punishment.
