An investigation has been launched after a train derailed outside West Ealing Station in west London.

The First Great Western train, en route from Swansea to London Paddington, came off the tracks between two stations at 2005 GMT.

Passengers waited patiently to be evacuated

There were no injuries and about 500 passengers were evacuated from the train.

The incident is expected to cause "significant disruption" to train services to and from Wales and the West Country on Monday morning.

BBC News Online's Andrew Walker, who was on the train, told of the moment it partly derailed.

"There was a great bump and a crash.

"We were all thrown in the air. It felt like the train was being dragged slightly."

Mr Walker said the neighbouring carriage was filled with dust following the impact.

"The people from the next carriage came into ours and they were panicking a bit at this stage."

Suffering shock

Speaking from the train, the 38-year-old said the neighbouring carriage was at an angle and slightly off the track.

But Mr Walker, who is in a wheelchair, said the mood of the train was calm and relaxed as passengers waited to be evacuated.

The derailment is expected to cause delays

John Roche, a spokesman for Great Western Railways told BBC News Online that it was a "minor derailment" of the 1630 GMT service.

"One grouping of wheels on one coach came off the track.

All of the train remained upright throughout the incident.

"There are no reports of anyone being injured but some people have suffered from shock," he said.

He estimated about 500 passengers would have been on board the busy Sunday evening train.

Mr Roche said it was too early to say what had caused the train to derail.

Severe delays

But he said it was fortunate no-one had been injured given that the train travels at 125mph along that track.

"Passengers are on the train and safe.

"The train was between two stations which has made it more of a problem than if it was in a station."

One set of carriage wheels came off the track

There was no sign of the derailment having been caused by vandalism, British Transport Police said.

Ambulance crews and police arrived by 2100 GMT to check all passengers were safe.

A spokesman told BBC News Online: "There will be a full investigation in conjunction with the Health and Safety Executive."

A spokesman for Railtrack said there would be "quite significant disruption" on Monday morning.

He said: "We are looking to run an amended timetable. We will be running trains but obviously there will be quite significant disruption."

Services will be diverted on to relief lines as they approach the scene of the accident, which occurred on the same stretch of track as the Southall tragedy, some 2.5 miles away.