POLICE last night ruled out a bomb blast as the cause of a train crash which killed four passengers and injured 34 yesterday.

The high-speed train, on the East Coast main line, came off the rails at more than 100mph, buckling carriages.

Hertfordshire Chief Constable Paul Acres, speaking only days after a bomb threat had been made, told a news conference: "We had investigated the potential that this was caused by an explosion, but this has now been ruled out."

He said: "There were early indications from witnesses that they heard the sound of an explosion, which we now believe was the sound of the impact."

The 12.10pm London King's Cross to Leeds GNER service derailed at Hatfield, Hertforshire, splitting the train in two and tearing a giant hole in the buffet car. Three carriages ended up on their side, with four others derailed.

Of the 200 passengers on the train, four were pronounced dead at the scene and 34 were taken to local hospitals.

Witnesses described scenes of "mayhem", with bodies by the track and people crying.

Doctors said that three of the casualties had serious, but not life-threatening, injuries.

As hospitals in the area instituted major incident procedures, firefighters used cutting equipment to free those trapped in the wreckage.

One of the passengers, Stephen Morgan, said of the aftermath: "Mayhem, the only thing I could say is mayhem - there were ladies crying."

In June 1998, another high-speed GNER train derailed on the same track just 20 miles away, slightly injuring nine people, the Health and Safety Executive said.

Possible causes of the crash, which is being investigated by the Railway Inspectorate, include vandalism or a faulty wheel or axle.

Kevin Walsh, of the Bedfordshire and Hertfordshire ambulance service, said: "When I approached the scene there was a multitude of people extracting themselves and walking down the road. When I actually reached the train itself, the passengers looked vacant, a shocked expression on their faces.

"Some people were using mobile phones to make contact and some people were walking slowly in a controlled line down towards the train station."

About 100 passengers were taken to a University of Hertfordshire conference centre in Hatfield where they were comforted and given refreshments.

Johnson Cox, director of operations for Railtrack, said at the crash scene: "Our thoughts and hearts go out to the families of the victims and to all those who have been injured."

Assistant chief constable Paul Nicholas said the scene was being kept secure while the bodies were removed. A search of the crash site was due to start at 8am today.

Tory leader William Hague said: "My first reaction, like most people, to the news of this terrible rail accident is 'how can this happen again?'

"Our thoughts and prayers are now with the injured and the relatives of those whose lives have been so suddenly snatched away."

Transport Minister Lord Macdonald praised the emergency services and said his thoughts were with the families of the victims. He had asked the HSE to provide an "urgent" report on the crash.

An emergency helpline was set up for worried friends and relatives on 08459 441 551.

Victims of previous train tragedies at Paddington and Southall were said last night to be devastated by the latest crash. Solicitor Stephen Acres, who represents families of victims of both disasters, said: "They can't believe it's happened again. This is the fourth one in a decade and it is absolutely unbelievable."