Seven people have been killed after two Metro trains collided in Washington DC.
The victims include the operator of the second train, Jeanice McMillan of Springfield, Virginia.
Carriages of both trains were ripped open and smashed together in the worst accident in the Metrorail system's 33-year history.
Washington fire spokesman Alan Etter said crews had to cut some people out of what he described as a "mass casualty event". Rescue workers propped steel ladders up to the upper train carriages to help survivors scramble to safety. Seats from the smashed carriages spilled out on to the track.
Mayor Adrian Fenty said officials are "going to let the investigation run its course" and said that hopefully the number of fatalities will not exceed seven by the end of the day.
Fenty also said that two people remain in critical condition in area hospitals. He said he has been told that their conditions are stable.
President Barack Obama sent his condolences to the victims of the crash. He said: "Michelle and I were saddened by the terrible accident in north east Washington DC. Our thoughts and prayers go out to the families and friends affected by this tragedy." The president also thanked rescue personnel who helped to save lives.
The crash, at around 5pm local time, took place on the system's red line, Metro's busiest, which runs below ground for much of its length but is at ground level at the accident site near the Maryland border in north east Washington.
Metro chief John Catoe said the first train stopped on the tracks, waiting for another to clear the station ahead, when the trailing train, one of the oldest in the Metro fleet, ran into it from behind. Officials would not say how fast the train was travelling at the time of the accident. The trains had pulled out of Takoma Park station and were heading in the direction of Fort Totten station.
More than 200 firefighters from Washington, Maryland and Virginia were involved.
