Six killed in US subway collision
Two rush-hour subway trains have collided in Washington DC, leaving at least six people dead and 76 injured.Carriages of one train came to rest on top of the other after hitting it from behind as it was stationary, although the cause is unclear, officials said.
The female driver of the moving train was among the dead.
The crash - the worst in 33 years of the Metro system - happened above ground between Fort Totten and Takoma Park at 1700 local time (2200 BST).
President Barack Obama said in a statement: "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.
"I want to thank the brave first responders who arrived immediately to save lives."
Washington mayor Adrian Fenty has visited the scene of the crash
Washington fire chief Dennis Rubin said approximately 200 firefighters were at the scene of the accident.
He said 76 people were treated at the scene and six of those were sent to hospital with critical injuries.
He said the majority were walking wounded.
The dead driver was named as Jeanice McMillan, 42, by the Associated Press (AP) and the Washington Post
Washington Mayor Adrian Fenty described it as "the deadliest accident in the history of our Metro train transit system".
He added: "We have to at this time continue to act and behave as a rescue scene."
BBC correspondent Richard Lister said it was possible people were still trapped in the lower of the two train carriages.
He said Mr Rubin had reported that parts of that carriage were 70 to 80% compressed.
'Ploughed into the back'
The general manager of the Washington subway, John Catoe, said the crash had happened as one train waited for another to clear a station ahead.
He said: "The next train came up behind [the waiting train] and, for reasons we do not know, ploughed into the back.
"We are committed to investigate this accident until we determine why this happened and what must be done to ensure it never happens again."
Both trains involved in the collision were heading in the direction of Washington rather than to the city's outlying areas.
This meant the trains were likely to have had less people on them, AP quoted Debbie Hersman of the National Transportation Safety Board (NTSB).
Passenger Jodie Wickett told CNN she had been sitting on one of the six-car trains, sending text messages on her phone, when she felt the impact.
We stopped and then it felt like an explosion... when we were hit it seemed like at full speed by the train behind us
She said: "From that point on, it happened so fast, I flew out of the seat and hit my head."
Ms Wickett said she stayed at the scene and tried to help.
She added: "People are just in very bad shape. The people that were hurt, the ones that could speak, were calling back as we called out to them.
"Lots of people were upset and crying, but there were no screams."
Another unnamed passenger said: "I was on the train that got hit. We stopped and then it felt like an explosion... when we were hit it seemed like at full speed by the train behind us.
"It was horrible. The second train - the first car was just absolutely shredded, the second car, the seats were out the window. It was awful."
Our correspondent added the accident had happened at the peak of rush hour, on what is a popular and busy commuter line.
The accident is the Metro network's first crash with a passenger fatality since 1982 when three people were killed in a derailment.