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
A Labour MP tipped as a possible candidate for London mayor has admitted crashing into a motorcylist her second accident in just over a year
The 48-year-old man was held on suspicion of theft from heritage and protected sites.
A Met Police officer was left red-faced after attempting to stop a cyclist riding along a dedicated cycle path.