City recorded a 14th consecutive Premier League win to climb 11 points clear of their closest challengers, and United boss Jose Mourinho was reportedly unhappy with the post-match celebrations of his opponents.
Mourinho and City goalkeeper Ederson were involved in a heated row in the tunnel which quickly escalated to involve a number of players and staff from both clubs, leaving City coach Mikel Arteta with a bloodied face.
Reports have now surfaced claiming that Lukaku was to blame for drawing the blood from Arteta after throwing a bottle during the fracas which hit the Spaniard.
An empty plastic bottle also reportedly struck the head of Mourinho, who had milk and water thrown at him during the melee.
Lukaku was criticised for his performance during the match itself as he drew another blank to make it just two goals in his last 14 outings for United.