About twenty firefighters battled a blaze at an office building in Milton that caused significant damage and saw one officer suffer smoke inhalation.

Crews were called to the Finchley Street address just before 2am after reports of a fire in a five-storey commercial building.

The blaze, in an office on the fifth floor, caused extensive damage to that level and smoke and water damage to other parts of the building.

Paramedics also treated a fire officer for minor smoke inhalation, an Emergency Management Queensland spokesman said.

The cause of the blaze is still unknown but fire investigators have arrived on the scene. No one was in the building at the time.

Police have closed Finchley Street to all traffic from Heussler Terrace to Black Street.