POLICE confirmed on Tuesday they were treating the blaze at Smithills School as arson.

Now they are planning to carrry out door-to-door inquiries in a bid to find the culprits.

Forensic investigators are examining shards of glass for fingerprints as they search for clues.

A spokesman for Greater Manchester Police said: "The fire is now officially being treated as arson and an inquiry has been launched."

The fire broke out in the east wing of the upper building of the school in Smithills Dean Road, Bolton, on Saturday morning. Three classrooms and a section of the roof were destroyed.

A spokesman for Greater Manchester Fire and Rescue Service said that investigators hoped to take fingerprints from shards of glass found at the scene.

"We have sent samples of glass to the police forensics team and we hope to have a result by the end of the week," he said.

"There is a history of vandalism and of youths drinking in the area and there have also been other small fires set near to the school in the past. Given that, its very much looking like this was a malicious fire."

He added that the blaze was started in a "normal" classroom where there was little chance of a fire starting through faulty electrical or IT equipment.

That classroom and two others were wrecked. A further six classrooms suffered smoke damage in the blaze, which broke out at 7.40am.

A total of 14 classrooms are out of use because of an adjoining staircase being put out of action.

Headteacher Ken Howell said the school would remain closed to pupils on Monday, January 9, although members of staff would be at work.

On Tuesday, January 10, Years 8, 9, 10 and 11 will return to school. But Year 7 will remain at home all next week. It is hoped all year groups will be back at school from Monday, January 16 and letters will be sent out to parents this week to confirm details.

It is hoped temporary classrooms will be brought in while the damage is repaired.

Mr Howell paid tribute to the work of firefighters who he said saved one of the schools main computer rooms.

But modern languages and media studies coursework is thought to have been ruined by the fire.

Anyone with information should call police on 0161 872 5050 or Crimestoppers on 0800 555111.

l The school says work for Year 7 pupils, who will not be able to return to school next week, will be available on the schools website www.smithills.bolton.sch.uk or from the school office from next Tuesday.