CHILDREN as young as 11 were last night being sought by police after a concrete slab was thrown onto a train from a bridge.

The driver had a narrow escape after being hit by the slab, which was dropped from a footbridge into his cab.

The 39-year-old was treated in hospital for neck and head injuries after the attack as the train travelled at 75mph along the East Coast Main Line.

Police said Thursday evening's incident could easily have ended in a murder inquiry because the 10lb slab had come within inches of hitting the driver on the head.

Detective Sergeant Brian Buddo, of British Transport Police, said: "The driver is a very, very fortunate individual. If it had hit him in the head, it would have killed him and we would have been looking at a murder investigation.

"In my opinion, this was a deliberate act of vandalism."

Three children, aged between 11 and 13, are being hunted by police.

The incident happened shortly after 8.45pm on the road bridge leading to Littleburn Industrial Estate, just off the A690, in Durham City.

The Northern Trains pacer train was travelling from Darlington to Newcastle, with the driver the only person on board.

As the train passed under the bridge, the driver noticed a youth wearing black clothing drop the piece of slab over the edge of the bridge parapet.

Moments later it crashed into the cab 20ft below, showering the driver with glass.

The driver suffered neck injuries, cuts and bruising and was taken to hospital in Newcastle. He was released after treatment.

His employers said he was too badly shaken by the incident to speak to the media.

Police suspect the missile may have bounced off the roof of the cab or the back of the driver's seat before hitting his head otherwise his injuries could have been considerably worse.

The train was yesterday taken to a depot in Heaton, Newcastle, where it was being examined by staff from regional train operator Northern.

A spokesman said: "Following an incident on Thursday evening involving a Darlington to Newcastle service, we are currently working with British Transport Police to catch three youths who threw a large rock at the train."

He added: "Unfortunately, incidents of this nature are not rare and we are committed to finding and prosecuting people who cause mindless vandalism."

Recent figures show that vandalism is increasing on the East Coast Main Line.

Earlier this week, up to £10m-worth of damage was caused when three cars caught alight on a freight train near Darlington, which may have been caused by stone-throwing youths sparking an electrical fault.

Darlington was named as the worst place for railway vandalism in the country, and among the worst for trespassing, in the Railway Crime Report 2004.

In the 48 hours after the report was released, there were a further 18 reports of trespassing on North-East railway lines.