SAFETY experts today launched an inquiry to discover how 13 people were hurt - two seriously - as two carriages hit each other on Blackpool's world famous Big One.

Blackpool Pleasure Beach was evacuated last night following the accident which happpened as the 87mph roller coaster was moving at just 2mph. The ride will remain closed tonight when the town celebrates the annual switch on of this year's illuminations.

Eleven of the casualties had minor whiplash injuries and two teenage boys, who were cut free from the roller coaster by emergency workers were kept in Blackpool Victoria Hospital overnight.

Anthony Rodgers, 13, is being treated for a badly broken leg and Anthony Constantine, 15, for back and rib injuries. Both boys live at St Anne's Road Children's Home in Blackpool.

Health and safety officers have launched an inquiry and said the ride is likely to be closed for some time. The rest of the Pleasure Beach was due to open for business as usual today.

David Cam, director and company secretary of the Pleasure Beach, said today that a full investigation was under way and that the Health and Safety Executive had been informed. He said: "The accident happened as one car was coming into the station and the other was just outside the station.

"We called in the HSE last night and we started our own investigation to find out exactly what happened. He added: "The cars have been slightly damaged. The nose of the cars are pointed so the second car has pushed a V-shaped dent into car one.

"We know that one car was sitting in the brakes outside the station, we don't know why.

"We do have a completely automated computer-controlled system which gives us the advantage of being able to download details of the braking system so we can find out precisely what happened in those seconds before the accident."

Inspector Steve Chapman, of Lancashire Police, said: "We can confirm there were eleven walking wounded with bruising and whiplash injuries.

"Two young males were trapped on the ride and they were freed and taken to hospital."

A spokesman for Lancashire Fire Brigade said: "The fire service were called to an incident around 8.45pm involving a crash on the Big One.

"When we arrived four people were trapped in a car at the station, two of them were released and the other two had to be released using specialist cutting equipment.

"The two boys were very distressed and in a great deal of pain. It took some time to release them.

"The station is around 30 feet from the ground and the two boys had to be lowered to the ground by a team using rope rescue techniques."

Restaurant worker Ali Akbar Rafsanjani, 26, from Bradford, was treated for whiplash. He said: "There were screams. I was knocked out for a few seconds and when I came to there was panic all around. It was chaos, it was really frightening."

In July, an 11-year-old boy, Christopher Sherratt, of Blackpool, plunged to his death from the Space Invaders ride at the Pleasure Beach, Britain's biggest free tourist attraction, with more than 7.5 million visitors through the gates annually.