The driver in control of a tram which crashed in Croydon, south London, may have "blacked out" and collapsed onto the controls, inadvertently causing the vehicle to speed up, a passenger has claimed.
The crash, which killed seven people and injured 50 others, was travelling at a "significantly higher speed than is permitted" when it careered off the track lines shortly after 6am GMT on Wednesday 9 November.
The two-carriage vehicle derailed at the Sandilands tram stop amidst torrential rain, with residents saying they heard a loud bang as the tram tipped over. The vehicle was being driven by a 42-year-old from Beckenham, who has been arrested on suspicion of manslaughter. The driver remains in police custody while the investigation continues.
Witnesses say that the tram was coming down towards a bend on a steep slope and, instead of turning, it carried on down the hill which flipped the vehicle at the entrance of a tunnel.
The crash left people trapped inside the tram with emergency workers frantically battling to free survivors in chaotic scenes. The Mayor of London, Sadiq Khan, visited the site while British prime minister Theresa May offered her "thoughts and prayers" to those affected.
The Rail Accident Investigation Branch (RAIB) said the tram derailed while negotiating a "sharp, left-hand curve", which has a speed limit of 12 mph. A spokesman said: "Initial indications suggest that the tram was travelling at a significantly higher speed than is permitted."
A passenger on board the tram said it seemed to speed up, with the driver allegedly telling a man that he had "blacked out". Father-of-four Martin Bamford told the Daily Mail: "When we were coming through the tunnel we were going at some speed and the tram was speeding up more and more.
"We were coming out of the tunnel and we hit the bend way too fast and the tram flipped. The tram was full mainly of people going to work. There was a girl who was on top of me and she did not look very much alive at all. She was bleeding all over the place and I don't think she made it.
"I looked around and there was just blood everywhere I was shouting through to the driver to ask him if he was okay. He was laying on his side and I asked him if he was okay. I think he was in his mid 30s or 40s. When we got out I asked the driver if he was okay and what happened and he just said to me: 'I think I blacked out'".
The London Ambulance Service confirmed that a further eight people suffered serious or life-threatening injuries following the crash, while a total of 51 injured citizens had been taken to two hospitals.
The British Transport Police (BTP) said it was investigating whether the driver had fallen asleep. Robin Smith, Assistant Chief Constable of the British Transport Police, told the BBC that this was being looked into alongside "a number of factors".