Four helicopters and at least 11 fire trucks are battling a blaze covering 100 hectares on Tiwai Pt, near Bluff in Southland.
Because of the seriousness of the fire and its proximity to the Tiwai Pt aluminium smelter two helicopters with night-vision equipment will remain in the air through the night, Fire and Emergency New Zealand media liaison officer Sally Chesterfield said.
Six ground crews will be present throughout the night as well.
The fire is not yet contained and several ground crews have been added to the 11 fire trucks and four helicopters already in attendance.
At 10pm the fire was 100m from the main powerlines that run to the Tiwai Pt aluminium smelter, and was 400m from the smelter itself.
The area is covered in dry native scrub, Chesterfield said.
A mobile command centre had been set up.
The fire alert was raised at 7.10pm. The cause is unclear at this point.