The buffet car had its roof peeled off like a sardine can

Passenger Justin Rowlatt

An investigation has been launched and British Transport Police say they cannot rule out the possibility of a terrorist attack or vandalism on the line.

Officers revealed they had received a bomb threat relating to the track between King's Cross and Peterborough on Sunday. However they stressed that injuries in the accident were not consistent with an explosion.

The 12.10 GNER service from King's Cross to Leeds skidded off the tracks south of Hatfield at more than 100mph.

Most of the passengers were described as walking wounded but 26 casualties were taken to the Queen Elizabeth II Hospital in Welwyn Garden City and seven to the Lister Hospital in Stevenage, Hertfordshire.

A surgeon from the QEII Hospital said one person had a spine fracture and four patients will stay overnight.

Hospital spokesman Mark Purcell added that the majority of casualties had suffered "lumps, bumps and fractures".

The roof of the buffet car was ripped off in the accident but the driver's cab was relatively undamaged and British Transport Police said officers were waiting to speak to the driver.

Stephen Morgan, a passenger on the train, told BBC News24 he had helped women off the train.

"I just heard a big bang and then just everything went - the train went over on its side.

"I grabbed the nearest thing I could grab to get myself a little bit of comfort, and luckily enough I came through all right.

'Mayhem'

"The door was on its side so we managed to get that open to get some air in there in case there was any fire.

"It was mayhem, with ladies crying. They could not get into the buffet car - it was all mangled - that's probably where the people died."

Emergency number

08459 441551

A Channel Four reporter Justin Rowlatt, who was travelling on the train described how it came off the rails and skidded along gravel at the side of the tracks.

"The roof had been completely ripped off the restaurant car and peeled away like a sardine can.

"The first class carriages have completely come off the rails."

BBC reporter Kate Williams said the train was lying in two halves, with the buffet car almost totally destroyed.

Vandalism

Hertfordshire police received a call at 1225BST and emergency services, including eight fire tenders, arrived at Welham Green, south of Hatfield, soon after.

The Health and Safety Executive said no other train was involved. It added that the crash site was a bad stretch of line for vandalism, but stressed there was no evidence that that was a cause of the crash.

Carriages toppled onto their sides

Railtrack spokesman Phil Heath told BBC News24 said the King's Cross train "was on the correct line, and the signalling equipment appeared to have been working normally".

In 1998, nine people were hurt when an Inter City train left the same track 25 miles further north at Sandy, Bedfordshire.

GNER spokesman Alan Hyde said: "We have to keep an open mind, our priorities are just with dealing with the incident as it unfolds.

"Our thoughts go out to the families of those involved."

Trains are leaving Kings Cross but are subject to delays.

The crash comes little more than a year after the Paddington rail disaster killed 31 people, putting rail safety at the top of the political agenda.

In a separate accident on Tuesday, a commuter train derailed after it hit a minibus on a level crossing at Egham, Surrey. No-one was badly injured.

Last week Deputy Prime Minister John Prescott said �60bn would be spent on rail safety over the next 10 years.

Hertfordshire Police have set up a helpline for members of the public seeking information on 08459 441551.