Firefighters have been working throughout Sunday to strengthen the containment lines around the Port Hills fire. Photo: CHRIS SKELTON
Helicopters battling the Port Hills blaze had to be grounded on Sunday due to a private drone being used in the area.
Fire and Emergency incident controller Steve Kennedy said at a media briefing on Sunday afternoon the drone was flying around the bottom of the hill, around the Cashmere Road area.
"Please, just keep away from the area we're working in. This morning we had to bring our helicopters down because they actually cannot fly when there's private drones flying around that area," he said.
Drones created a "huge safety risk" for helicopter pilots, he said.
Police Inspector Ash Tabb said drones could not operate within four kilometres of any aircraft taking off or landing.
Each time a drone was spotted in the airspace, the helicopters had to be grounded for about 45 minutes or an hour, but the exact length of time depended on how long the drone was flying.
"Those pilots are working incredibly hard in a very technical role and that's the last thing we need."
Police were actively investigating the incident, Tabb said.
A small number of people had also been trying to access walking tracks in the area, which put both themselves and emergency services at risk, he said.
He reiterated calls for the public to stay away for everyone's safety.
Fire and Emergency NZ incident controller Steve Kennedy, Police Inspector Ash Tabb and Anne Colombus from Christchurch City Council and Civil Defence deliver an update on the Port Hills fire. Photo: RNZ/Nathan Mckinnon
The bushfire broke out on Wednesday and has since burnt through more than 650 hectares, destroying one home and causing mass evacuations.
It had been contained as of this weekend, with almost all residents allowed to return home.
However, firefighters were continuing to stamp out hotspots on old "skid sites" - left over from forestry logging operations - which needed heavy machinery to dig them out.
Additional hotspots had been identified by drones and a helicopter overnight and at first light on Sunday.
Kennedy said Fire and Emergency only operated its drones overnight, so if any members of the public saw drones in the area during the day, it was "not one of ours".
He said the skid site hotspots could take the better part of a day to stamp out, but there were some smaller hotspots that only took half an hour.
He said the firefighters - some of whom came from as far away as Nelson and Tasman - had been putting in a "huge effort".
"Up on the hills where they're digging and working away, it's hot, hard work."
Fire and Emergency operations manager Rob Hands surveys the damage done by the blaze. Photo: CHRIS SKELTON
Meanwhile, Fire and Emergency was wary that strong winds were forecast for Monday, with gusts of up to 80kph expected, Kennedy said.
Firefighters had been working to strengthen the containment lines on Sunday before those winds arrived.
The fire had been contained within a 24-kilometre perimeter. Crews wanted to make containment lines at least 50 metres wide, Kennedy said.
MetService meteorologist Mark Todd earlier said severe gales were predicted for the Canterbury high country on Monday and a strong wind watch was in place.
"We're not expecting severe gales to come down to the plains but there will be strong and gusty northwesterly winds in exposed places around the Christchurch area during the course of Monday as that front approaches."
Kennedy earlier said there was a chance some people would need to be evacuated again due to the strong winds.
Christchurch City Council fire controller Neville Riley said the local state of emergency remained in place until further notice.
Riley said further evacuations were "the last thing we want to do" but the state of emergency would enable them to do so if necessary.
There were 86 firefighters and other personnel at the site on Sunday, supported by diggers and bulldozers, while five helicopters were also available.