A tram that derailed in Croydon, south London, killing seven people, was travelling at three and a half times the speed limit, investigators have found.
The Rail Accident Investigation Branch (RAIB) said the tram, with about 60 people on board, was travelling 70km/h in a 19km/h zone.
In its interim report, it said there was no evidence of any defects or obstructions on the track, nor was there a braking system malfunction.
The tram derailed about 6.10am on 9 November, shortly after coming out of a tunnel with an 80km/h speed limit.
Transport for London (TFL) has offered to pay for the funerals of those who died, but was criticised after it was revealed the families were not told this in person.
Initial analysis showed the driver, Alfred Dorris, braked after coming out of the tunnel, but only enough to reduce his speed from 80km/h to 70km/h. The tram travelled 25m before stopping.
Police arrested Mr Dorris, 42, from south-east London, on suspicion of manslaughter. He was released on bail until May.
It was understood establishing whether Mr Dorris, who has worked for First Group since 2008, was asleep or blacked out were lines of inquiry.
The seven people killed in the crash were Dane Chinnery, 19, Philip Logan, 52, Philip Seary, 57, Dorota Rynkiewicz, 35, and Robert Huxley, 63, all from New Addington, and Mark Smith, 35 and Donald Collett, 62, both from Croydon.
A further 51 people were taken to hospital, with eight of them suffering serious or life-threatening injuries.
The RAIB said it had advised London Trams and Tram Operations Ltd to put speed restrictions in place before the bend out of the tunnel.
London transport commissioner Mike Brown said: "We will follow the RAIB's advice and, before service is resumed, will implement additional temporary speed restrictions and associated signage near Sandilands to supplement existing safety arrangements.
"We are continuing to carry out a thorough safety assessment and are taking the advice of an independent panel of tram experts.
"We will only resume services for the local community once that rigorous assurance process has been completed."
The report also found:
At the time of the accident it was dark and raining heavily
CCTV was not working at the time of the derailment
The right side of the tram, which made contact with the ground, was severely damaged
The tram would have had to start braking 180m before the 19km/h speed restriction sign to get the speed down
Aslef, the train drivers' union, said it was "clear that the lack of adequate safety systems were at the root of this dreadful accident".