• Confrontation in tunnel and changing rooms after derby match • City coach Mikel Arteta left with blood streaming down his face • FA asks clubs for observations and police ready to act on any complaint

Police officers and stewards had to separate up to 20 players and members of staff from Manchester United and City after an extraordinary bust-up in which bottles and punches were thrown and Mikel Arteta, one of Pep Guardiola’s assistants, was left with blood streaming down his face.

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The incidents have prompted an inquiry from the Football Association, which has asked both clubs for their observations after establishing that the referee did not witness what happened. The governing body could sanction clubs and/or players or staff. Greater Manchester police will launch an investigation if they receive a complaint but will not act unilaterally. As of Monday morning they had not received a complaint from United, City or any alleged victim.

Arteta’s eyebrow was split open during a melee in a narrow corridor outside City’s dressing room and there were unconfirmed reports that another member of Guardiola’s backroom staff needed medical treatment after a confrontation sparked by José Mourinho apparently telling the victorious players to keep their music down.

Mourinho became embroiled in a row with Ederson, City’s Brazilian goalkeeper, who was standing just inside the dressing-room door and the two started shouting insults at one another in Portuguese. Mourinho is said to have accused Ederson of play-acting to waste time and then reverted to English, screaming “you fucking show respect. Who are you?”



Other players became involved and Romelu Lukaku was said to be prominently involved as the confrontation escalated into something much more serious, described by one person on the scene as being reminiscent of a pub fight. Early accounts indicate it was a much more serious incident than the infamous “Battle of the Buffet” in 2004 when Arsenal were the opponents and Sir Alex Ferguson was hit by flying pizza slices.

Q&A What was the Battle of the Buffet? Show Hide Long-standing hostilities reached a new boiling point in October 2004, when Sir Alex Ferguson's Manchester United ended Arsenal's 49-game unbeaten sequence in the Premiership, with United winning 2-0. The action was tempestuous on the field, but it was after the match that the sparks, and the food, really flew. In a tunnel scuffle between players and staff on both sides, a slice of pizza was hurled at Ferguson. Ashley Cole described the shock of the incident in his autobiography: 'This slice of pizza came flying over my head and hit Fergie straight in the mush … all mouths gawped to see this pizza slip off this famous, puce face and roll down his nice black suit.' Earlier in 2017, Cesc Fabregàs admitted it was he who tossed the slice: 'I was like, I want to get in but I don't know how to and I threw … just threw it. I apologise Sir Alex, really didn't mean to do that.' Photograph: Monty Rakusen/Cultura RF

There were also reports that Mourinho was struck by a plastic bottle, as well as being squirted with milk, although that has not been confirmed and the Guardian has been told he escaped lightly despite being in the middle of it. Once everything had calmed down, Mourinho went into the referee’s room to voice his complaints to Michael Oliver about the incident when Ander Herrera was booked for going down under a challenge from Nicolas Otamendi in the penalty area.

Facebook Twitter Pinterest Ederson celebrates in the tunnel after Manchester City’s win. Photograph: Victoria Haydn/Man City via Getty Images

Mourinho then emerged to do his television interviews and there was no sign of him needing to dry off. He did not make any reference to what had happened during all his media work.

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Arteta, meanwhile, was being assessed in the City dressing room after being caught in the crossfire. United’s players are understood to feel like the noise from the away dressing room was provocatively loud and, with the door continually being opened, Mourinho appears to have been asking more respect to be shown to the losing team.

As the confrontation escalated, Sergio Agüero and Bernardo Silva were caught on the outside looking in, having not been inside the dressing room when it started. However, other City players were clearly incensed by Mourinho’s behaviour and the fact that several players, most notably Lukaku, had become involved. There are always two police officers in the Old Trafford tunnel after games and eventually they helped to restore peace.