Suspicious house fire in Sydney's west

A house in Sydney's west has been destroyed in a suspicious fire in the middle of the night.

Fire crews arrived at the Doonside blaze about 3.30am on Wednesday to find the unoccupied house well alight.

Police have been told a window was heard being smashing in the vicinity about the same time as the fire, and a crime scene has been set up at the Astral Drive property.