A fire has damaged a two-storey wooden building at Windmill Park in Mt Eden in Auckland.

The Fire Service was called to the fire in clubrooms at tennis courts in Windmill Road about 2.20pm on Sunday, a spokesman said.

The building was well ablaze when they arrived, and at the peak of the fire five appliances were used to fight it.

The fire is "pretty much out", and firefighters are cleaning up at the scene, the spokesman said.

A fire investigator is at the scene and the fire has been referred to police because it may be suspicious.

The building is badly damaged.