No formal action will be taken by the Football Association (FA) over an incident in the tunnel following Manchester City's Premier League win at Manchester United.
Players and staff from both sides reportedly clashed after City's 2-1 derby victory at Old Trafford earlier this month.
Referee Michael Oliver did not witness the incident and did not file a report, leaving the FA to investigate the skirmish, which allegedly began when United manager Jose Mourinho approached the City dressing room to complain about music being played loudly.
"Following a review of the evidence provided by the clubs and independent eyewitnesses, the FA will be taking no formal action," an FA statement released on Thursday said.
Both clubs had been asked for their observations and were granted additional time to respond to the governing body.
Separately, Mourinho was asked to explain comments he made to the media in the build-up to the derby, when the Portuguese appeared to accuse City of gamesmanship, saying: "A little bit of wind and they fall."
Following the December 10 derby - which City won thanks to goals from David Silva and Nicolas Otamendi to move 11 points clear of United in the Premier League table - Mourinho explained his part in the incident.
"The only thing I can say is it was just a question of diversity; diversity in behaviours, diversity in education," Mourinho, who was reportedly splashed with milk during the fracas, told reporters when asked about the alleged flashpoint. "Nothing more than that. That's all I'm going to say."
In response to Mourinho's complaint, City coach Pep Guardiola insisted his players had not set out to rile their neighbours following the victory.
"Our intention was not that [to upset United]. Our intention was to celebrate inside the locker room our happiness, because we were happy," he said.
"If people can't understand that then I am sorry. We were so happy, we won a derby and wanted to celebrate in the locker room.
"If in that we offend Man United – not just one player, not Jose, not the players – Man United, I apologise."