The Croydon tram service has reopened, just over a week after the derailment in which seven people died.
Investigators have said the tram was travelling at three-and-a-half times the speed limit when the crash happened near the Sandilands stop.
The Rail Accident Investigation Branch (RAIB) said the tram, which was carrying about 60 people, was doing 43.5mph in a 12mph zone.
British Transport Police said a Facebook post from last week which said that a tram "lifted onto one side at 40 mph" near the same location as the crash "will now form one of our lines of inquiry".
The Rail Accident Investigation Branch (RAIB) has launched a witness appeal. Anyone who was on the tram or has information relevant to the accident is asked to complete an incident report form on the RAIB's website. An interim report into what happened will be published by the RAIB next week, with a final report, including any safety recommendations, coming at the conclusion of the investigation.
A tram driver who appears to fall asleep at the wheel in a video filmed by a commuter has been suspended.
Transport for London has offered to pay for the funerals of the seven people killed in the tram crash in Croydon.
The Rail Accident boss from Network Rail says that investigators have 'downloaded data from a black box' from the derailed Croydon tram.