Firefighters were "planning for the worst" last night as a huge scrub fire burned across Great Barrier Island, forcing the evacuation of homes, businesses and a medical centre.
The island's full complement of trained firefighters - about 40 people - backed by three helicopters with monsoon buckets were battling the 8ha blaze, which flared up about 1.20pm at the northeastern end of the island, near Claris Airport.
Late last evening the medical centre in Claris and four homes attached to it were evacuated as a precaution, Auckland Rural Fire spokesman Bryan Cartelle said.
Up to 20 homes and factories had been evacuated earlier in the day.
No one was in the medical centre at the time and St John had received no reports of fire-related injuries from the island.
As night fell, plumes of smoke could be seen many kilometres from the island.
From above, a trail of damage several kilometres long could be seen cutting through the eastern side of the island.
Many of those evacuated gathered near Claris Airport to watch the fire's progress.
Mr Cartelle said there was a lot of smoke, making it difficult to access the fire last night.
"The boys have got a lot more confidence now [in bringing the fire under control] ... but it doesn't take much once nightfall comes, and if we haven't got it buttoned up at the head of the fire then we need to keep chasing it for some time."
Initial reports of the fire being suspicious could not be confirmed, said fire communications shift manager Jaron Phillips.
He was also unable to confirm that yesterday's emergency was caused by a vegetation fire tackled on Sunday reigniting.
Fire officers would remain on duty overnight, said Mr Cartelle. The safest approach would be to continue dampening the hottest part during the hours of darkness.
The wind was expected to shift in a more favourable direction and drop in speed, he said.
"That's a bonus, we've got to plan for the worst," he said.
Claris Airport operations manager "Greeney" said the onshore wind had pushed the fire inland.
At 7.30pm, firefighters were strug-gling with smoke preventing the helicopters from getting in front of the fire, he said.
"The helicopters can't get in front of the smokescreen because it's too thick for them to come in and try and drop the water at the head of the fire.
"They're just trying to contain what is happening," he said.
Claris Airport closed about 3pm and inbound flights were directed to the island's Okiwi airstrip.
Passengers due to take a 5pm flight from Claris Airport were bussed to the Okiwi airstrip and left from there.
Great Barrier Community Board chairman Paul Downie said the fire was devastating.
He advised residents to prepare a bag of necessary items such as their driving licence and credit cards in case more buildings needed to be evacuated quickly.
The manager of the Crossroads Backpackers Lodge in Claris, Katie Langford, said they were getting ready to leave if the fire got too close.
"We haven't been evacuated yet but we're just on standby," she said.
Meanwhile, a scrub fire in northern Kaipara "escalated quite a bit" last night.
Mr Phillips said it covered 35ha to 40ha at 5.30pm but was covering about 180ha three hours later.
Four helicopters and rural fire-fighters were continuing to battle the blaze, which was not threatening any homes.