AN investigation was under way last night after a truck carrying 18 people crashed and overturned into a river at one of the North-East's most popular tourist attractions.

Passengers had a lucky escape when the all-terrain articulated vehicle at Diggerland, in County Durham, failed to stop at the bottom of a steep 20-metre hill, despite having tough tank-type tyre treads.

The truck, which was being used to give visitors a tour of the site at Langley Park, toppled over as the driver tried to negotiate a right-angle bend.

It fell 8ft and rolled over before coming to rest in the shallow water of the River Browney.

The driver escaped unhurt and the passengers' seatbelts protected them from life-threatening injuries.

Twelve people were hurt, including six children and two toddlers, in the accident at 12.45pm yesterday. They were taken to the University Hospital of North Durham, in Durham City, for treatment.

Two people were stretchered out of the trailer while the others crossed the river unaided to get to dry land.

The most seriously hurt was a six-year-old boy, from Northumberland, who needed an emergency operation for a severe fracture to his foot.

A 35-year-old woman was also kept in hospital overnight with suspected broken ribs.

One man discharged himself from hospital before being seen by doctors and the remaining visitors were released after treatment for cuts and bruises.

Acting Inspector Eddie Bell, of Consett Police, who attended the scene, said the trailer came to rest on the weir with the tractor-part facing downstream.

He said: "I would not have liked to go over that drop so it would have very scary for the passengers. There would have been moments when they were thinking 'help' because it is a big drop.

"Some of them would have landed in the water, so you can imagine it was quite an ordeal."

Acting Insp Bell added: "One suggestion is that the engine cut out, reducing its braking capability because the servos wouldn't work.

"Other suggestions include driver error or some other mechanical failure but we have to keep an open mind."

The Health and Safety Executive (HSE) has taken over the investigation.

An HSE spokesman said: "The vehicle has been pulled out of the water and is in quarantine waiting for a mechanical engineering specialist who will come out first thing in the morning to examine the vehicle.

"We have issued a prohibition notice on this machine and another which is used at Diggerland.

"We will also be looking at the degree of the slope they came down to find out if that had anything to do with it or whether it was some thing else."

The park is expected to be open today as usual and will be visited by the company's operations director.

No one from the company was available to commentlast night.

It is thought to be the first accident of its kind at the theme park, which gives young people the chance to get behind the wheel of mechanical diggers.

The £2m adventure park opened just over three years ago and promotes itself as an "educational day out with a difference".

A disclaimer at the attraction reads: "No liability can be accepted for any loss or damage to vehicles, property or personnel, howsoever caused."