Ten fire engines are working to contain a blaze in the south Auckland suburb of Takanini.
The fire, which broke out around 4.30pm, started in the wall of a room at 219 Great South Road, in Takanini, containing painting materials.
One person had been treated by St John ambulance crews after inhaling paint fumes.
Fire and Emergency New Zealand shift manager Colin Underdown said it appeared flammable painting material had burst into flames.
"Ten fire engines plus two more specialist appliances are there," Underdown said.
Underdown said hazardous material specialists were at the scene.