The suspicious fire at Buninyong Public School left six classrooms with significant damage estimated at more than $750,000.

Police are appealing for witnesses and believe the blaze was deliberately lit.

About 12.20am Sunday, emergency services were called to Myall Street, after reports a school was on fire.

One of the buildings was completely destroyed in the blaze, Fire and Rescue NSW station officer Mathew Havercroft said.

“The entire structure was already well alight on arrival,” he said.

Dubbo and Delroy firefighters in four trucks attended the scene.

They set up defensive fire-fighting and there was no immediate threat to other buildings, he said.

Officers from Orana Local Area Command attended and assisted Fire and Rescue NSW as they extinguished the blaze.

The fire caused significant damage to six classrooms including a special education room with disability ramp access and the canteen, police said on Sunday.

No one was injured.

The damage caused by the fire is estimated at more than $750,000, police say.

A crime scene was established and on Sunday was being examined by specialist forensic officers.

“Investigators believe the fire was deliberately lit and are appealing for anyone with information to come forward,” NSW Police said in a statement.

A brief will be prepared for the information of the Coroner.

The school community is on holidays until July 18.

On Sunday investigators continued their work at the scene, a blackened mess marked off by police tape.

The smell of fire and burnt assets remained hours after the flames were put out.