Manchester United and Manchester City will face no action over an incident that took place in the tunnel after the derby on 10 December, the Football Association has said.
United boss Jose Mourinho had water and milk thrown at him and City coach Mikel Arteta suffered a cut head during a post-match row.
The FA said it considered evidence from “clubs and independent eyewitnesses”.
Mourinho will also not face action from the FA over his pre-match comments.
However, the FA has reminded the Portuguese that any further public comments about match officials may result in disciplinary action.
The tunnel incident arose after what United viewed as an excessive celebration following City’s 2-1 win at Old Trafford, which sent them 11 points clear at the top of the Premier League.
City’s players celebrated in front of their fans after the final whistle.
After the players headed down the tunnel, it is understood that Mourinho made his feelings known outside the visitors’ dressing room as he made his way to post-match interviews.
A one-pint milk carton – which had been in the City dressing room for tea and coffee – was thrown at Mourinho. The United manager did not get splattered but a member of his staff was.
City’s Brazil goalkeeper Ederson and Mourinho exchanged angry words in Portuguese – but Mourinho carried out his post-match media engagements as normal and made no mention of the row.
Arteta was left with a cut after he was hit by a plastic drinks bottle, but it is not known who threw it and sources from both clubs said no punches were thrown.