UPDATE: A fire that broke out at St Columba’s Catholic high school in the Blue Mountains, west of Sydney, is being treated as arson.

The historic sandstone building was also damaged when devastating bushfires swept through the area in October 2013.

Fire crews were alerted to the fire in Springwood shortly after 5am (AEST) on Sunday and took several hours to bring it under control.

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Crews are now carefully mopping up as the school is in dense bushland.

They arrived to find a large building well alight with four classrooms on fire.

Superintendent Tom Cooper from Fire and Rescue New South Wales (FRNSW) said the school was isolated and the fire could have been burning for some time.

He said it took some time for crews to find where the smoke was coming from.

“The school is situated is bushland roughly halfway between Winmalee and the township of Springwood so it’s very well isolated,” he said.

“We believe that this fire may have been well developed prior to the fire brigades from either RFS or Fire and Rescue attending.”

It is not yet known how the fire started but it comes almost a year to the day after the nearby community of Winmalee was devastated by bushfires.

The school’s acting assistant principal Mark Sattler said the loss of several classrooms was devastating.

“We feel very much for our community, for the kids and the teachers but we’re very thankful that there’s been no loss of life,” he said.

“Again we’re waiting from the fire authorities for a full assessment but we do know that we’ve lost several specialist areas, art rooms, industrial technology rooms, a hospitality area.

“So that’s going to mean a great deal to people in terms of the kind of learning that’s possible in those areas.”

Fire takes hold at St Columba’s Catholic College. Photo: Fire and Rescue NSW

Blue Mountains Mayor Mark Greenhill said it was a major blow to local residents.

“There was some damage to this school in the fires last year and of course the damage this morning is quite extensive,” he said.

“I’ve been onto the site and it’s truly sad. This is a school that’s resisted and been affected by fire before and to see it in the state it’s in this morning is very sad.”

Police have appealed for any witnesses to come forward.

The Catholic Education Office says it will fence off dangerous areas and bring in demountables before HSC exams begin.

The NSW government will also consider granting special consideration to ensure students’ marks are not adversely affected.