Eleven Tube passengers were taken to hospital today after a London Tube train derailed, possibly due to a "bale of material" that fell on the tracks from an underground storeroom.

Hundreds of passengers were trapped in a tunnel after the accident on the westbound Central line between Mile End and Bethnal Green in the east of the capital just after 9am.

It is thought six carriages left the track, but still remained in an upright position.

A total of 37 people were injured, of which 11 needed hospital treatment for minor injuries including panic attacks and an ankle injury.

Passenger Jacqui McElroy, 34, said the train "started to rock unbelievably, really violently".

"The carriage filled with smoke and we could see sparks and there was a smell of electrical burning as the driver was braking.

"People were shouting and the driver's voice sounded really shaky - he said he did not know what we had gone over, but that we had derailed."

Ms McElroy, a make-up artist, said the driver walked through the carriage trying to calm passengers before the Transport Police arrived around 20 minutes later.

It took almost two hours before all 350 passengers on the derailed train, as well as another 350 trapped on one behind it, have been led out along the track to Mile End.

Metronet, which maintains the tracks, said initial reports suggested "a bale of material became dislodged from its licensed storage position in a tunnel cross-passage".

The company announced it would check all similar storage facilities along the tracks "as a precaution" before the start of service tomorrow morning.

Transport for London (TfL) confirmed investigators were looking at reports of an "obstruction of the line".

It ordered an immediate review of storage facilities on the Underground.

Howard Collins, deputy chief operating officer for London Underground, said: "It looks like material, some form of sheeting.

"Initial reports from the driver are he saw something white flapping in the tunnel, before he hit it. There was a loud noise and then he hit the brakes."

The Rail Accident Investigation Bureau has begun an investigation into the incident.

Superintendent Phil Trendall of the British Transport Police said: "There is no indication of any terrorist attack."

The accident caused chaos in the morning rush-hour for the 560,000 passengers who daily use the Central line.

Almost the entire eastern half of the line - between Liverpool Street and Leytonstone - was shut down, while Mile End and Bethnal Green stations were closed to services on all lines.

Richard Porter, operations manager for London Ambulance, said the rescue operation was "very swift", although the conditions underground made people "uncomfortable and sweaty".

"The temperature above ground was about 21C (70F). That can rise by 5-10C (when) below," he said.