A fire at a disused primary school may have been started deliberately just weeks after pupils were decanted out of their classrooms and into temporary premises.

More than 35 firefighters were called to the blaze at St Mary's Primary in Larkhall at around 2.30am yesterday.

The force of the fire was so great that a subsequent gas leak in the basement built up so much pressure in the surrounding sewer network it blew a drain cover 30 feet into the air.

Councillor Lesley McDonald said police believe the fire may have been started maliciously but the theory had yet to be proved.

Councillor McDonald said: "Things are at an early stage but it seems to have been started deliberately. If true, I find that absolutely disgusting. The fire at St Mary's is the second fire at a Larkhall school in 10 days."

Strathclyde Police said that inquiries into the blaze were continuing.

Fire crews from Motherwell, Hamilton and Bellshill fought the fire for more than five hours with a spokesman for Strathclyde Fire and Rescue adding that part of the school collapsed, but a section with listed status was saved.

Crews remain at the scene, dampening down the building with South Lanarkshire Council's building control department inspecting the premises.