A busy dual carriageway was brought to a halt when a huge crack appeared across the road.

The chasm, which is 2ft wide and 10ft deep, split Sunderland from the neighbouring town of Houghton-le-Spring.

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

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

Highways bosses ordered workmen to begin digging up two lanes of the road and earth-moving equipment revealed the geological fault is 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.

"The position of this fault - in line with a busy carriageway - is very worrying.

"We're not sure of the exact cause of the problem and we're 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 added: "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's a process that will take time, but we're aware this line is moving vertically and sideways."

Workmen will spend the weekend filling the hole and repatching the fracture.