A Brisbane factory is still smouldering and remains a crime scene after a fire sent toxic plumes of smoke across the city's north on Sunday.

It took 50 firefighters to stop the blaze at a Virginia factory from spreading to neighbouring businesses, and authorities were forced to declare an emergency situation and set up an exclusion zone.

The declaration was revoked about 11pm but firefighters continue to monitor the smouldering site, and a crime scene has been declared as investigators work to determine what caused the fire.

Amazing video from our chopper over the top of the Virginia workshop fire. Stay clear of smoke could have asbestos @9NewsQueensland pic.twitter.com/FtRBRqxSnx

— Darren Curtis (@DarrenCurtis9) September 24, 2017

"Initial inquiries suggest around 3.30pm police and emergency services attended a large fire that had broken out in an industrial building on Pritchard Road," the police report states.

"An emergency situation was declared and an exclusion zone was put in place. The PSPA was revoked at 11.10pm.

"While the fire is now out, there is some smoke haze in the area with fire crews still at the site hosing down the area to prevent re-ignition.

A crime scene has been declared, and scientific officers and fire investigators will attend the scene tomorrow (Monday) morning to determine whether they are able to safely investigate the cause."

With AAP