A fire that destroyed a public library at a school in Cambridgeshire was accidental.
Forensic experts have completed their investigation into the blaze at Sawston Village College, and think it was caused by a hot air gun.
More than 1,000 pupils returned to the classroom this week, after Thursday's evacuation.
An investigation's underway, after a building at a college in Cambridgeshire was gutted by fire.
The blaze broke out yesterday afternoon on the site of Sawston Village College. Dozens of firefighters were called to the scene from Hertfordshire and Essex as well as Cambridgeshire.
Firefighters are dealing with a blaze at Sawston Village College in Cambridgeshire.
It broke out just after two o'clock this afternoon.
Eight crews from across the county are at the scene. The fire is in a single storey building in the oldest part of the school.