FIRE crews launched a major operation this morning after a lorry spilt gallons of an unknown chemical substance on a busy County Durham road.

At about 10.15am this morning six appliances and two specialist hazardous substance appliances were called to the A167, at the Newton Aycliffe interchange, above the A1M.

Steve Wharton, assistant community safety manager for Durham and Darlington Fire and Rescue service said the lorry had spilt about ten chemical drums.

"We didn't know what was in the drums so we had to treat the incident at its worst case scenario," said Mr Wharton.

"The driver would have been carrying information but he didn't know he had lost the load and had continued driving.

"They were plastic drums which burst like water bombs when they hit the road so any information on the actual drums was destroyed.

"We still don't know exactly what was in the drums yet but we have satisfied ourselves that it is a low hazard substance and we have scaled the operation back."

One lane of the A167 was closed and motorists experienced some delays but the A1M was unaffected.