Manchester United and Manchester City have been given until 6pm on December 15 to provide observations on the alleged fracas following Sunday’s derby at Old Trafford.
Runaway Premier League leaders City opened up an 11-point gap over second-placed United with their 2-1 weekend win.
Victory sparked mass celebrations from City, and United are understood to have taken exception to how their visitors conducted themselves in and around the dressing room area.
Milk and water are claimed to have been thrown at United boss Jose Mourinho after a reported confrontation with City goalkeeper Ederson, leading to an alleged altercation involving up to 20 players and staff in a crowded corridor.
The Football Association had been in touch with both clubs, but will now allow more time for additional information to be provided.
“Manchester United and Manchester City have both been given extra time to provide their observations following reports of an incident after Sunday’s game. They now have until 6pm on Friday 15 December,” the FA said in a statement.