Investigators are trying to find out how a woman fell under train at a south London Tube station during the morning rush hour.
Transport for London said the woman fell between the train and the tracks at Clapham South at 08:00 GMT.
The woman, who is reportedly in her 20s, was taken to hospital and her injuries are "non life-threatening".
Eyewitnesses claimed she was either "dragged" or "pushed". Police said it was not being treated as suspicious.
On Twitter @SJPTelly said: "Just been evacuated from a tube at Clapham South after a poor woman was dragged underneath it. Horrible."
Firefighters had to use specialist equipment to free the woman from the northbound Northern line platform.
On Twitter, Cristina Squires said: "I saw firemen trying to get her out. They have to jack up the train."
Other commuters spoke of the woman being "pushed" and questioned whether the platform was overcrowded.
James Callen tweeted: "I've just seen a woman get pushed under a tube by accident at Clapham South."
London Underground said at the time of the incident the platform was not overcrowded and a full investigation was under way into what happened.
A spokesman for British Transport Police (BTP) said they believed the woman had "come into contact with the train".
In a statement, the force said: "The incident is not being treated as suspicious.
"Inquiries are ongoing to establish exactly what happened."
London Fire Brigade sent two fire engines and a fire rescue unit to the station and used a "scoop stretcher" to rescue the woman.
LU said there was no service between Morden and Kennington for about an hour after the incident, which also caused delays to the rest of the line.
Nigel Holness, London Underground's operations director, said: "Just before 8am this morning a passenger fell between the train and tracks at Clapham South station.
"The passenger has been recovered by the emergency services with non-life-threatening injuries"