US train crash toll rises to nine
At least nine people have been killed and 70 injured in a subway train collision in Washington DC.
Carriages of one train came to rest on top of the other after the collision near a station, officials said.
The female driver of the moving train - which crashed into the back of a stationary train - was among the dead.
The crash - the worst in the 33 years of the Metro system - happened above ground between Fort Totten and Takoma Park at 1700 local time (2200 BST).
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.
She said: "From that point on, it happened so fast, I flew out of the seat and hit my head."
Washington mayor Adrian Fenty has visited the scene of the crash
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."
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 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.
Mr Rubin said parts of that carriage were 70 to 80% compressed, and that rescuers did not know if there were still more bodies to be found.
I thought it was like the train bombings in London. There was smoke and dust everywhere
Passenger Abra Jeffers
In pictures: US train crash
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 fewer people on them, AP quoted Debbie Hersman of the National Transportation Safety Board (NTSB).
Busy commuter line
"I was on the train that got hit. I thought it was an explosion," passenger Abra Jeffers, 25, told the AFP news agency. "I thought it was like the train bombings in London. There was smoke and dust everywhere."
Passenger Theroza Doshi told the Reuters news agency: "It just happened. There was no slowing down of the train, just a jerk."
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.