Police are investigating a suspicious blaze in a building that houses the National Distribution Union office in Auckland.
The fire broke out about 12.45am on Sunday in a bus belonging to the union that was parked in the basement of the two-storey building in Onehunga. The building also houses a drycleaning business.
Guards were placed at the scene overnight.
The union's national secretary Laila Harre says the bus, used during pickets and strikes, is destroyed, the garage suffered damage and the union's offices had to be broken into to check the fire had not spread.
Although police and the fire service are treating the fire as suspicious, Ms Harre does not believe there was any political motivation behind the blaze. The union plans to replace the burnt-out bus.
Five fire appliances and 26 firefighters attended the blaze.