FIREFIGHTERS have warned parents to make sure they know their children's whereabouts after a fire started by youths in Oswaldtwistle caused a gas cylinder to explode.

The old pickle factory, in Stanhill Road, went up in flames at around 1am today after someone lit a fire on the roof of the derelict building. They fled as firefighters arrived.

Crews from Blackburn were first on the scene and arrived to find the roof and a section of the first floor well alight. Earlier, nearby residents had reported an explosion and firefighters today confirmed a propane cylinder in the building had exploded, blasting out sections of the roof.

Ronnie Gorton, 75, of Stanhill Road, said: "It gets broken into every week. They live in there, some of them. My wife heard a bang, like a bomb, at about ten past one."

Neighbour Euna Goode, 77, said: "My daughter came and told me the fire brigade were up here.

"From my bedroom window I could see the blue lights."

Eight firefighters, wearing breathing apparatus, used an aerial ladder platform to extinguish the blaze, which took over two hours to bring under control.

Asbestos was found to be present in the building and firefighters were today having to send their equipment away to be specially cleaned.

The roof and the rest of the two stories were left badly damaged. Inspectors were due at the scene today to assess the building's condition.

Residents have reported seeing a group of teenagers riding away on bikes, and today firefighters said the building had seen problems in the past with children playing there and lighting fires.

Aidan Fortune, station officer at Blackburn fire station, said: "We would urge all parents to ensure they know what their children are doing and alert them of the dangers of playing inside these buildings. If we have got gas cylinders involved then there is every chance that they will not be coming out alive and certainly not walking out of the building."