A FIRE which destroyed part of a private school in Helensburgh and left one firefighter injured may have been started deliberately, it has emerged.

Police yesterday confirmed they were treating as suspicious the early morning blaze which swept through the St Bride's building of Lomond School, causing damage which an insurance company representative on site estimated could amount to more than #1m.

A firefighter who suffered burns to the back of his neck later re-ceived hospital treatment but a spokesman for the brigade said his injuries were not serious.

The blaze was discovered shortly after 3am and the senior master, Mr Ian McKellar, who was called to the scene, said he had been able to see the flames from his bedroom window in Roseneath.

''At that time, it looked as if someone had dropped a landmine in the middle of the town,'' he said.

''We understand that the fire started in the headmaster's office and quickly spread to the upper floor of the building.

''A preliminary assess-ment indicates that six classrooms have been completely destroyed, together with the headmaster's room and the depute headmaster's room. Part of the building will have to be demolished,'' he said.

Mr McKellar could not comment on how the fire may have started but confirmed that Strathclyde Police were investigating.

Although the affected part of the site was closed, classes were continuing yesterday in another building.