A BUSY dual carriageway was brought to a halt when a large crack appeared across the road.

The chasm, which is 2ft wide and 10ft deep, cut off the principal route between Sunderland and neighbouring Houghton-le-Spring.

Experts believe it may be due to old mine workings opening up beneath the road surface.

The crack caused chaos on Friday as the route, the A690, is one of the busiest roads into the city, with 17,200 vehicles using it every day.

Highways bosses ordered workers to begin digging up two lanes of the road and earth-moving equipment revealed that the geological fault was still on the move.

Geologist Bryan Young said: "This could continue for years to come. I think the council will have to carry out repair after repair because of the position of the fault. Its position - in line with a busy carriageway - is very worrying.

"We are not sure of the exact cause of the problem and we are working closely with the city council to see what can be done."

Geologists think the fractures have reappeared because old mineworkings, hundreds of feet underground, are deteriorating, producing fissures on the surface.

Mr Young said: "We carried out a radar survey of the area to find out how big the crack was. Our study has found these cracks and holes often appear almost overnight.

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