It will likely be several hours before a fire which is burning through Department of Conservation land in Southland can be brought under control.
A contractor is believed to have accidentally started the fire at Tiwai Peninsular, near Bluff, about 4.30pm yesterday.
Rural Fire Officer Sue Peterson said about 930ha of wetlands had been burnt between Awarua Bay and the sea.
Helicopters had "knocked down the worst of the fire front", but it was not expected to be fully under control for several hours, she said.
A team of three helicopters and two ground crews worked through the night until being stood down at 2.30am. Reinforcements joined them when they resumed work at first light this morning.
Ms Peterson said the fire was moving slowly to the east, away from the Tiwai Point aluminium smelter. There was little wind and conditions were favourable to firefighters.
The area was home to protected red tussock and other native plants, plus several species of unique invertebrates.
A full investigation into the fire would be launched once it had been put out, Ms Peterson said.
NZPA