AN investigation is underway after an arson attack on a derelict mill.

The fire happened at around 1am at the building off Grange Road in Blackburn.

Four fire crews attended the incident for around an hour and used breathing apparatus and hose reels to extinguish the blaze.

Nobody was injured in the fire which was reported by a passerby dialling 999.

A fire service spokesman said: "An investigation is underway into the incident which we believe was started deliberately.

"It was quite a big fire, there was a lot of smoke, it could have spread to the whole building if we didn't get there in time."