By 7.45pm the building had partially collapsed, and asbestos had been found at the site. Decontamination procedures were being set up.
A northern fire communications spokesman said multiple calls were received about 6.30pm, reporting the fire which was in a building with a basement and one level, measuring about 50m by 20m, and used for boat manufacturing and fibreglass laminating.
It was not known whether there was anyone in the building, and firefighters were in defensive mode as they tried to bring it under control.
Later a spokeswoman told NZPA there were 13 appliances and about 52 firefighters at the scene.
"We're currently rotating crews due to the heat and humidity," she said.
It was not known how long it would take to bring the fire under control but she thought it would be a long job.
There had not been any injuries reported.
"Due to the fact that there has been asbestos located we have notified the public health services and the Department of Labour workplace inspector, which is standard procedure," she said.
The Southern Motorway at Penrose on-off ramp was closed.
TV3 reported people as far away as Whangaparaoa in the north of Auckland had reported seeing black smoke in the sky.
