Emergency services are working to extinguish a blaze in an industrial building in the Auckland suburb of Ellerslie.
A fire communications spokesperson said the blaze had been upgraded to a level three alarm and said the fire was "well involved in the building".
Around 15 trucks and 60 firemen are headed to the scene.
A spokeswoman for St John said an ambulance was called to the scene at about 3.45pm as a precaution.
The ambulance has since been stood down.
Workers in neighbouring buildings were calm when the Herald contacted them.
A worker in the Goddards Cartage building opposite said there were several fire trucks outside, but he could not see much of the blaze.
Another person working in a building behind Global Fasteners said they had heard sirens, but were not too worried about the blaze nearby.
"Somebody said they could smell smoke just before and we thought: 'Oh, there must be a fire'. But we're okay."
A selection of cartoons from Herald cartoonist Rod Emmerson over the past year