UPDATE: Police investigating after suspicious blaze destroys Sydney primary school

Detectives are investigating a suspicious fire that gutted a primary school in Sydney's west overnight.

Firefighters were called to Badgerys Creek Primary School about midnight after the building was engulfed by flames.

A police spokesman said the school had been broken into, along with several other buildings on the property.

He said forensic and Rural Fire Service investigators are now at the scene and the fire is being treated as suspicious.

Much of the school building was gutted by the blaze.

The school has been empty since the start of last year when it was permanently closed.