Police are investigating after a private drone flying near the Port Hills fire grounded fire crews helicopters for up to an hour.

Police were actively investigating the drone incident in conjunction with the Civil Aviation Authority, said Canterbury Police Inspector Ash Tabb.

Drones were not permitted to operate within four kilometres of any aircraft taking off or landing, which means most of the Christchurch city around the area.

“That actually brings our firefighting capability down with the helicopters having to go down, those pilots are working incredibly hard in a very technical role and that’s the last thing they need,” said Tabb.

“For the members of the public, if you do see a drone in the air, please bring 111 immediately.”

Fire and Emergency New Zealand Incident Controller Steve Kennedy, Canterbury Police Inspector Ash Tabb, and Anne Colombus from Christchurch City Council and Civil Defence. Photo / Ben Tomsett

Fire and Emergency New Zealand Incident Controller Steve Kennedy said the private drone being flown in the area was a huge safety risk for fire crews, and was probably one of the biggest risks they had faced at the Port Hills to date.

Fenz had been using drones over night to map the fire ground and help identify any hotspots for fire crews to work on tomorrow, though members of the public would be able to identify private drones as Fenz were not flying throughout the day, he said.

He said he was unsure of the exact amount of time helicopters were grounded for, but it was likely from 45 minutes to an hour.

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The remains of the Port Hills fire still smoulders. Photo / FENZ

Fenz drones would be flying again tonight from 9pm, he said.

Tabb said a there had been several people attempting to access walking tracks in the area, putting themselves and emergency services at risk.

“We’re saying to the community, it’s just for a short period of time, can we just keep out of the area. It makes it easier for firefighters and makes it easier for the police and all the other agencies just to get on with trying to reduce the risk to the community,” he said.

Kennedy said the thermal imaging drones had mapped 60 areas that we need to be working on, with 35 of those on the perimeter of the fire.

“We’re putting all our resources into those hotspots, and especially in some areas that could be problematic,” he said.

left to right, Lee Reihana (City Care firefighter), John Hytongue (City Care firefighter), and Stephen Robson (Peel Forest Volunteer firefighter) and other firefighters continue their efforts to dampen down remaining hot spots and create a buffer zone around the 24km perimeter of the fire in the Port Hills. Photo / Chris Skelton

He said firefighters were trying to get a lot of the hotspots cleaned up today before the expected wind change this evening.

At its height, over 100 firefighters, 28 fire engines, 14 helicopters, and two planes were battling the fire on Thursday. The fire spread over an area of about 700ha.

The cause of the fire has has yet to be identified, though all evacuees have been allowed to return home.

A charity organisation called the Christchurch Foundation has opened a fund to assist in replanting of trees in the impacted areas.