AN investigation was under way today after a blaze at a Haslingden mill which could have been caused by a stray firework.

More than 30 firefighters tackled the blaze at JH Birtwistle's textile mill in Grane Road after a fire ripped through the roof space of a disused office block.

Fire crews were called to the scene shortly before 7pm yesterday.

The blaze caused extensive damage to the roof of the two-story block but did not spread to the main part of the mill. Fire investigators were set to return to the scene today.