FIRE crews spent nearly 24 hours cooling explosive gas cylinders after a fire destroyed a disused warehouse.

Police were last night waiting for the building to be secured before they begin their investigations, but fire officers believe the blaze was started deliberately.

Three fire engines and an aerial platform were needed to battle the fire at the building in Whessoe Road, Darlington, which raged from 9pm on Monday until after 2am on Tuesday.

The site needed to be monitored round the clock until last night, because the building was unstable and to make sure acetylene gas cylinders were kept at a safe temperature.

Dane Rollo, of Darlington Fire Service, said they were treating the blaze as suspicious.

"There has been a spate of nuisance fires in that area caused by youths recently," said Mr Rollo.

"It looks like someone got access to the premises from the rear and started a fire in the main building.

"A fire investigation will start in the morning, but we have to make the building safe first because there are parts that could collapse. The roof is in a very bad way."

Officers at Darlington Borough Council are trying to trace the owners of the building, which once belonged to a demolition company.

Whessoe Road was closed while fire crews dealt with the flames, and again last night while the roof was secured.

Mr Rollo said the damage could have been much worse if gas cylinders in the building had exploded.

"We are still cooling an acetylene cylinder," he said. "It is a particularly explosive gas used for welding. If the cylinders are damaged or exposed to direct flames, they can explode.

"We had to set up a 100m cordon and close the road and we will continue to cool parts of the building until it is safe to move."

Inspector Steven Steen, of Darlington police, said last night: "We have not had a chance to carry out any investigations yet because we have to wait for 24 hours before we can go in. We are not able to tell if it is arson, but the fire brigade have indicated that it looks suspicious."