Blaze damages Brisbane businesses

A large fire has caused extensive damage to a number of businesses at an industrial site in Brisbane.

The blaze broke out about 4.30am at Boolarra Street at Hemmant.

Dozens of firefighters are at the scene, with their efforts focused on a large warehouse.

Police have declared a crime scene, with forensic officers to inspect the site when it's safe.

Nearby residents have been told to keep door and windows closed due to heavy smoke.