Early reports suggest that the fire was started by a discarded cigarette or an electrical fault near one of the top bunks in a second-class compartment.

An attendant pulled the emergency cord on the 2130 from Penzance and the train stopped, half a mile from its next scheduled halt at Taunton, Somerset at 0248 BST (0148 GMT).

It is the worst accident on Britain's railways since November 1967, when 49 people died in a derailment at Hither Green, south London.

Fire-fighters arrived within four minutes, but their efforts were hampered by internal and external locked doors.

Speaking in a BBC radio interview, British Rail's chief operating manager, William Bradshaw, has confirmed that it is company policy to lock doors connecting carriages, but not external doors while the train is in motion.

He said many passengers choose to lock the doors on their compartments for security whilst they are asleep.

Dealing with casualties

Local residents from Fairwater Close in Taunton went to help survivors from the train and provided tea, blankets and comfort in their homes.

The injured were transferred to hospitals in Taunton.

All of the 31 dead or injured were in the front two carriages of the 12 coach train.

Most of the bodies were found in the sleeping compartments and all but one was from the UK.

Forensic scientists state that the likely cause of death was asphyxiation rather than burns.

Accident investigators will examine safety procedures and materials used by British Rail.

They currently operate 350 sleeper carriages - none of which is less than 18 years old.

MPs have already called for an immediate end to the practice of locking external doors.

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