SEVEN people have died and around 50 others were injured after a tram overturned in south London early on 9 November.
Some of the survivors were seriously hurt.
The 42-year old tram driver has been arrested on suspicion of manslaughter, and he is helping with police enquiries.
Transport for London said the accident had occurred at 06.13. The tram had been carrying early-morning commuters towards Croydon town centre, and overturned alongside a sharp curve near the Sandilands stop.
The Rail Accident Investigation Branch said the tram was travelling at a 'significantly higher speed than is permitted'. The limit on the curve is 20km/h, and investigators are now looking for causes. Unconfirmed reports have suggested the driver could have lost consciousness.
The Mayor of London Sadiq Khan and the Prime Minister Theresa May have both issued messages of sympathy.
The Mayor said: "My thoughts and prayers are with the friends and families of those who have lost their lives today, and everyone involved in this incident.
"I am in close contact with the emergency services and Transport for London, who are working extremely hard under very difficult circumstances to get the situation under control and treat those who have been injured."
Tram services east of Croydon town centre remain disrupted for the time being.