NSW unit block evacuated after car fire

Around 75 people have been evacuated from a six-storey unit block after several cars caught alight in the building's basement carpark in Sydney's northwest.

The blaze at Telopea completely destroyed two cars and damaged two others with firefighters extinguishing it just after 6am on Wednesday.

All floors of the housing commission building were evacuated after smoke spread throughout the building and three people were treated with smoke inhalation at the scene, a spokesman from Fire and Rescue NSW told AAP.

Investigators are working to determine the cause of the fire.