A FIRE that destroyed cars being carried on a freight train could have caused up to £10m in damage.

An investigation into how three Nissan cars - being transported from the company's factory in Washington, Wearside - caught fire on the East Coast Main Line is under way.

The incident happened on Monday night. Firefighters received a report of a vehicle alight on a freight train just outside Darlington.

But the blaze quickly spread to two adjacent cars and late-night passengers at the town's Bank Top station were stunned to see the blazing vehicles speed past.

The train came to a halt about a mile outside the station after a signal worker told the driver of the blaze just after 8.45pm.

Some of the windows on the cars were smashed. One theory is that youths, who often hurl stones at the car transporter trains on Tyneside, may have caused an electrical fault.

Dave Turnbull, community safety manager for Durham Fire Brigade, said the train is thought to have come under attack in the Jarrow area. And he said the damage caused could have been as much as £10m.

He said: "The potential loss was in the region of £10m, when you consider there was a diesel loco worth about £1.25m and all the supplementary rolling stock," he said.

"The East Coast Main Line's 25,000-volt overhead electrical cables were just above the train.

"It could have had quite a devastating effect, and it must have been quite spectacular to any bystanders."

He added: "The crews did a fantastic job in extinguishing the blaze, which let us get on to carry out an investigation."

Firefighters were at the scene for about an hour-and-a-half, and the line was re-opened at 10.20pm.

The train was carrying hundreds of left-hand drive vehicles, bound for the Continental.

A Network Rail spokeswoman said: "That section of the line is electrified, so we had to turn that off for people's safety.

"That was our first priority, along with stopping trains in the vicinity."