Fire crews are cautiously optimistic they have finally gained the upper hand over a huge blaze that has been burning on Great Barrier Island through the week.

However, a south-easterly wind could fan flames again, Principal Rural Fire Officer Bryan Cartelle said.

The Navy had been drafted in to help the large contingent battling fires on the Hauraki Gulf island as the threat of poor weekend weather kept dozens of firefighters on high alert.

The fire has been burning since Monday and has destroyed more than 100ha of bush.


But Mr Cartelle said they were in a "good position".

Charred scrub was still smoking "and where there's smoke there's fire", so fire crews were remaining vigilant, he said.

"We're strengthening some containment lines.

"The south east breeze does pump through here and we've got some additional strategies in case it does start to break out - we've got some retardant and we've still got two helicopters on the island."

Yesterday the HMNZS Otago has been "rapidly redeployed" from a training exercise at sea to help with the efforts on the island.

It delivered five tonnes of equipment and supplies at the request of the Department of Conservation (DoC).

The deployment was requested as Defence Minister Jonathan Coleman said he was "very concerned" by two fires that started during the army's live ammunition training on tinder-dry military land at Waiouru.

One destroyed 350ha of scrub on training land around the army base.


Five civilian helicopters and an RNZAF helicopter fought the blaze, which was last night contained.

News of the fire came as Selwyn District Council principal rural fire officer Wilson Brown estimated the Defence Force would face a bill of about $200,000 for the cost of tackling a major blaze ignited by grenade training at the Burnham camp near Christchurch on Wednesday.

It covered about 50ha and required 60 firefighters, six helicopters with monsoon buckets, 18 ground-based appliances and 40 police officers to fight it.

Canterbury conditions were the "worst seen for a number of years", according to area fire safety officer Graham Davies. "The guys who are returning from Australia [fighting bush fires] are being called into action as soon as they get back."

Fire Service northern communications shift manager Steve Smith said the "very dry" conditions showed no signs of abating.

"We can't stress it enough: you just have to be so careful," Mr Smith said. "People need to be extremely vigilant and careful of what they're doing."