One passenger has died and 83 others taken to hospital after a Washington Metro train filled with smoke on Monday.
The Virginia-Bound Yellow Line train had just left the L'Enfant Plaza station when it abruptly stopped about 45 metres into the tunnel.
The darkened carriages quickly filled up with smoke, and some passengers said they waited up to an hour to be rescued.
Witnesses described how passengers were choking, and some lost consciousness.
According to the Guardian, passenger Jonathan Rogers was quoted by The Washington Post as saying: "It started to get scary pretty quick. People started praying. Smoke was coming in pretty steadily."
Passenger Saleh Damiger said: "It was a lot of smoke. We couldn't see each other. We felt like we were almost going to die."
According to the Sydney Morning Herald, Metro General Manager Richard Sarles, told reporters on Monday night that the cause of the smoke had not been determined.
"We have one fatality, a woman who was in distress on the train, which I'm very sorry to report," he said. "And my heart goes out to her family."
Eugene Jones, the interim chief of the DC Fire and Emergency Medical Services, said the length of time people waited to be rescued was "nothing like" the length of time described, and said they wanted to be sure the subway's electrified third rail had been deactivated.
He added: "While the power may have been turned off to the track bed where the firefighters would go into make rescues, they heard trains running on the lower level of the station.
"So in their mind, they wanted to make sure that before they put people on the track bed that the power was actually off."
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