Firefighters work to get upper hand on Bridge Hill blaze

A wildfire burning in the Canterbury high country has grown to almost 1000 hectares and destroyed an old forest service hut, as firefighters take advantage of favourable weather conditions to try to bring the blaze under control.

State Highway 73 linking Canterbury and the West Coast has reopened to escorted convoys, with 10 helicopters, two planes and 86 firefighters involved in work to suppress the fire that tore through grass, scrub and wilding pines near Castle Hill village.

Fire crews are expected to take a week to stamp out the fire in steep terrain, with a team of three fire investigators examining the scene to try to find the cause.

There will be seven crews monitoring the Bridge Hill fire on Friday tonight, with winds forecasted to strengthen overnight, incident commander Brian Keown said.

"It's important we keep on top of the fire tonight as we are close to containing it," he said.

"We hope to have containment completed tomorrow before the extreme fire danger day on Sunday."

Saturday will see an increase in ground crews and a decrease in aerial support to five helicopters and no fixed-wing aircraft.

Fire and Emergency Canterbury district commander Dave Stackhouse said Holloway Lodge - a former New Zealand Forest Service hut near the peak of Bridge Hill - was destroyed by the 980ha fire, as well as fences at Flock Hill station.

While the fire was not under control, he said "benign" conditions had helped crews make good progress ahead of stronger winds forecast early next week.

"We are aided by really good weather today and over the next two days with the south-west and mild wind conditions. It's really important for us, because we can really get in there with our firefighters.

"We can't rest on our laurels, however, if the wind conditions come up we need to increase our resources and that restricts our air attack option.

"We estimate we'll be here for at least seven days, it's quite a deep-seated fire in places so it's going to require a lot of manpower, a lot of firefighting effort, a lot of hard work on the hill country, a lot of steep terrain and a lot of thick vegetation to work around."

There was no current threat to Castle Hill village, although residents were briefed at a community meeting about precautions in the event of a flare-up.

Crews had spread a line of fire retardant in remote areas along the 17km perimeter of the fire. People should expect to see smoke in the area for the next two to three days.

Stackhouse said fire investigators would examine the topography, weather and fire behaviour.

"They basically track the fire back with a whole lot of burn indicators matching the topography... and come to a point of origin and then they eliminate a hypothesis of ignition factors."

Stackhouse said Canterbury was likely to move into a restricted fire season from next week, which meant fire by permit only, and a prohibited season by Christmas.

Three schools were evacuated from camps in the area as a precaution on Thursday - two were staying at the Environmental Education Centre and the other at Forest Lodge.

Ray and Maree Goldring were among a handful of people who stayed at Castle Hill village on Thursday night.

Ray Goldring said they were ready to evacuate if the fire threat worsened.

"I reasoned that with the amount of green grassland between us and the fire that the chance of it getting here was pretty remote, but we had all our equipment ready to go, both cars loaded up. We were cautious," he said.

"When you look at the devastation out here, it's really bad. It only takes a careless spark to set this sort of thing going. As the summer gets hotter and drier, the risk is also increasing."

Maree Goldring said the damage was beyond anything she could have imagined.

"We've known this area for 40 years and a lot of the area that was so beautiful is now just black, but it has taken out quite a few wilding pines, which is a plus."

Goldring said she was worried about the threat to the Environmental Education Centre at Craigieburn overnight.

"We found out this morning and have just seen photos of the fact that the fire went right up to it, but miraculously it's okay, so that was a big relief."

Environment Canterbury's Rich Langley said a considerable amount of work had been done since 2016 to control wilding conifers in the Craigieburn area, populated by regenerating and sprayed dead-standing trees.

"Without the control work there would be an incredible amount of fuel there for this fire. The dead-standing trees do burn easily, but certainly a closed-canopy forest spreads fire more quickly and ferociously."