Detective Chief Inspector Iain Miller said: "There were two groups of men who came together at the station as the train arrived. Two people tried to board the train, eight people tried to get off the train. There was a bit of an altercation which spilled onto the platform.
The result of that altercation was that one of the men was punched and fell between the moving train and the platform, that resulted in his death. There were at least eight people involved, other than the two witnesses.
We need more of those people to come forward and anyone else who was at the station or around the station at that time, between 11.40pm and midnight.
We have a lot of CCTV to trawl both on the train and in and around the station. That's being done by officers from British Transport Police.
More top news
Police have stepped up patrols after a woman in her 40s was "dragged to the ground" in a park in east London.
Families living near Heathrow say they are supporting a group of activists facing jail for chaining themselves to the airport's runway.
Police were called to break up a "large fight" which involved a baseball bat, a man dislocating his shoulder and three arrests.