GEOLOGISTS believe it could be weeks before the results of a survey will find the cause of cracks under the surface of a busy stretch of road in the North-East.

Experts used specialist equipment to carry out a close inspection of the A690 Dur-ham to Sunderland road, at Houghton Cut, Houghton-le-Spring.

The dual carriageway was closed for six hours on Sunday to allow the geological survey to be carried out safely.

Cracks first appeared in the road three years ago, but became deeper and wider in the summer.

Although repairs have been made, a geological fault under the road is believed to be still active, possibly as a legacy of mining activities in the area over the past two centuries.

Geologist Brian Young said studies of the road so far had revealed that the cracks could appear without warning.

"We've got markers dotted along the fault line, to monitor movements on the surface," he said. "It's a process that will take time, but we're aware this line is moving vertically and sideways."

Mr Young said the exercise charts movement to discover if there is a void space at some depth under the surface.

He has already forecast that the road may be subject to constant repairs as and when cracks surface.