Fire flares again damaging Qld unit block

About 80 people have been forced to flee a Brisbane unit block after the same apartment caught fire twice in eight hours.

The apartment was still under police guard after the first fire on Thursday when flames again took hold about 1.30am on Friday.

But this time the blaze spread, damaging a number of floors at the Chermside property.

Everyone got out safely, but some residents could be displaced for some time.

"About eight hours after the (first) fire had been extinguished police were still guarding the crime scene when the fire alarms in the unit went off again," a police spokesman told ABC radio.

The unit block was well alight when firefighters reached the scene.

Investigations continue.