LONDON (AP) _ Two trains collided near London's Paddington Station during the height of rush hour this morning, emergency services said. More than 100 people were injured, at least 17 of them seriously, a hospital reported.

Police said four people were confirmed dead.

At least one train reportedly derailed, fire broke out and more than a dozen fire engines and 70 firefighters went to the scene along with a stream of ambulances.

There were ``100 plus'' walking wounded and 17 people with serious injuries, said Joseph Gannon, general manager at St. Mary's Hospital. He had been notified of four people still trapped in the wreckage.

Chief Inspector Brian Gosden of the British Transport Police said that a ``great number'' of passengers _ possibly up to 100 _ remained trapped.

Scotland Yard said only that there were ``seriously injured and walking wounded.''

``There were really badly hurt people, badly burnt people. Some people have been impaled by seats,'' passenger Amelia Bane said.

The collision occurred about two miles from Paddington, near Ladbroke Grove.

``I was reading a book and found myself crashing into the person opposite me. The train was going over and over and over, and people were thrown onto the floor,'' passenger Mark Rogers said.

``People were screaming, a person pretty clearly dead, a woman who was thrown out of the train,'' he said.

Passenger Wolfgang Schmidt said, ``I can't see how many people are still in the carriages. The inside of the carriages are not burning but there are still people trapped,'' he told Sky TV News.

A spokesman for First Great Western Trains said the accident happened at 8:11 a.m. and involved its high-speed train from Cheltenham, in western England and a Thames Trains train heading to Bedwyn, Wiltshire, west of London.

The accident happened on the same stretch of line as the September 1997 Southall rail crash that killed seven people injured 150.

``There are a number of people I think fairly seriously injured on my side of the track. A lot of people are sitting stunned,'' said BBC Radio reporter Phil Longman, who was on board one of the trains.

``Firemen with listening equipment are listening to the side of the train,'' he said. ``There are 60 or 70 emergency service vehicles here.''

One engine and a front carriage were on their sides, he said.

``The next carriage has lifted up about eight feet and is pointing at the sky.''

Witness Mark Palmer said he was in the street when he heard a ``huge explosion lasting for about 15 seconds, followed by billowing smoke.''

Initially he thought the nearby supermarket had exploded.

He said one of the engines and one of the carriages were burned out and lying on their sides. Many of the other carriages had jack-knifed.

``It looks just horrendous. Rescuers are pulling people out of the wreckage _ there are dozens of ambulances and fire engines.''

Longman, the BBC reporter, said after the initial bang ``the train seemed to leap in the air.''

``There was another bang and I was flung forward, and I saw a piece of wreckage to the side of the window ... I thought the wreckage was going to come through the window.

``The guard came on the Tannoy (speaker system) and told people to walk to the back of the train. You could hear him calling out for help from the emergency services. He said `major emergency, major emergency.'''

The passengers panicked when they could not the doors opened, but Longman broke a window with an emergency hammer, he said. The passengers then began lowering women and the elderly to the track.

Asked if it was a head-on crash, Longman said: ``I understand from hearing other people that the Thames Train was not quite head-on.

``I think we hit on an angle, on the side of the Thames Train.''

Witness Emma Rippon told BBC radio, ``There was huge bang'' and that she had spoken to one man who had managed to escape from the wreckage.

``He said he was standing in the front carriage and suddenly it slowed a little bit and then (there was) a big explosion. A fire started immediately and the smoke was unbelievable,'' she said.

Emergency services were treating casualties at a supermarket near the crash scene, but a spokesman for the store did not know how many injured were there.