State Highway 1 at the top of the country has reopened as good weather conditions helped in the fight of a 400ha scrub fire, but the blaze is not yet contained.

Helicopters and ground crews have been battling the fire, in highly flammable scrub, since Tuesday afternoon.

The danger saw the highway shut between Te Paki Stream Road and Cape Reinga on Wednesday morning.

But light winds and a favourable wind direction on Thursday saw “things going according to plan” and there were no further flare-ups during the day, said Fire and Emergency incident controller Rory Renwick.

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Waka Kotahi NZ Transport Agency said the road was open on Thursday afternoon.

Renwick estimated it would take another three to six days before the fire was contained, and that could only be confirmed with thermal imagery.

The fire broke out on Tuesday afternoon about 5km from the famous Cape Reinga lighthouse but moved as close as 1.5km to the site, Renwick said.​

However, on Thursday, offshore winds were favourable for protecting the iconic site, he said.

“If the wind is to turn back in that direction, it will be a concern.”

About 40 ground crew​ were flown into the fire site early on Thursday, as the steep terrain has no roads and is inaccessible even to four-wheel-drives and quad vehicles, Renwick said.

Seven helicopters with monsoon buckets will also work with the firefighters on the ground.

Renwick said the plan for Friday was very similar, although some ground crews would be able to walk to their sites.

The hardest part of the fire is its large perimeter, with the 400ha fire area burnt in a patchy way, creating a large perimeter of about 12km, he said.

“At this stage, it’s a slog. There’s a lot of ground to cover,” he said.

“We’re focusing on the edge where there’s unburnt fuel but because the edge is so long, we’ve got a lot of work to do in the coming days.”

The fire is through highly flammable mānuka, kānuka and gorse – all of which can burn even when there is no drought, Renwick said.

Cape Reinga/Te Rerenga Wairua is a place of cultural, environmental and recreational significance, especially to Ngāti Kuri iwi who alerted firefighters to the blaze and had been proactive in firefighting efforts.

It is known by Māori as the place where spirits last set foot on the Land of the Long White Cloud before making their way to their ancestral homeland of Hawaiki.

Fire and Emergency’s Northland district manager Wipari Henwood said the fire broke out near a walking track and an investigator would look at the cause.

The area is under a restricted fire season.