Nottingham Forest and Derby County are said to be investigating an incident which took place after Tuesday night's Carabao Cup clash at the City Ground.
There appeared to be an altercation on the pitch following the Reds' 3-0 win over their rivals.
It happened while Derby's substitutes were warming down and members of the Forest ground staff were tending to the playing surface.
The two managers, Sabri Lamouchi and Phillip Cocu, were both giving post-match interviews to the media at pitchside at the time.
It is understood by Derbyshire Live the two clubs are in dialogue as they look to establish exactly what happened.
Albert Adomah, Joe Lolley and Joao Carvalho were all on target for the Reds as they claimed a comfortable victory in the second round tie on home soil.
