Helicopters were called into help battle a major fire in Christchurch's Port Hills that claimed a small cabin and forced dozens of people to evacuate their homes.
Now authorities have issued a health warning as smoke continues to billow across parts of the city.
The fire has burnt through about 25 hectares of land above Hillsborough since fire crews were called just after 11pm.
People had to be evacuated from Avoca Valley Rd and Port Hills Rd.
Civil Defence was co-ordinating accommodation at St Martin's School Hall for any evacuees who needed assistance.
Residents evacuated from Port Hills Rd still couldn't return to their properties, but those from Avoca Valley Rd could, Fire and Emergency NZ (Fenz) Area Commander Dave Stackhouse said.
No more evacuations were planned.
The flyover looked positive, Stackhouse said.
"Our crews did a fantastic job stopping the fire from spreading up the hills and potentially impacting homes.
"Our priority this morning is to keep it within the area we have currently contained it to.
"The weather is on our side, with only light winds forecast; this should help us in our work throughout today."
They had some "good positive leads" about where the fire began and how but would not be disclosing that at this stage, Stackhouse said.
They would be looking into reports fireworks were an ignition source, along with "all other sources", he said.
The fire was fuelled by "dense vegetation" of pine trees, gorse and scrubland, Stackhouse said.
Nearby resident Isabelle Thompson said they were woken to sirens about 12am, and at 12.30am received a knock at the door from a police officer telling them they needed to evacuate.
"The whole hill was glowing in the night, and a lot of people were out watching."
People were not panicked, she said.
Newstalk ZB's Mike Yardley was at the scene about 7.30am, and said he could not see any flames, just a lot of smoke.
"There is a considerable amount of smoke coming out of Avoca Valley. It is very much a vegetation fire, with white, wispy smoke."
He had spoken to a resident who had been evacuated overnight. She said no houses had been sacrificed nor were in any danger.
Canterbury District Health Board has issued a public health warning for the smoke.
There was potential that sensitive groups – such as those with heart or lung conditions, pregnant women, young children and the elderly – could experience symptoms like coughing, shortness of breath or eye, nose and throat irritation.
Medical officer of health Dr Cheryl Brunton said people affected by the smoke should close windows and doors, and reduce outdoor exercise.
"The advice to people experiencing any health issues from the Port Hills fires is to phone their own GP team," Brunton said.
"After hours, and when they're closed, a team or nurses is ready to take your call."
Police were investigating after reports a flare was seen over the Port Hills before Wednesday's fires began.
A spokeswoman this morning said police were assisting with cordons and working with Fenz to determine the circumstances of the fire, but it was too soon to comment on any potential cause.
Nobody had been taken into custody in relation to the fire, she said, but did not respond to questions from the Herald about if anybody was being spoken to.
The spokeswoman also said it was too early to say if the fire was suspicious.
Stackhouse said earlier this morning at the height of the fire 15 appliances and crews were deployed to combat the fire.
He said 50 firefighters were on the ground and focusing on protecting structures along Port Hills Rd. They were working to stop the fire from spreading further up the hill.
Stackhouse said they would get a good understanding of the fire at first light today.
Two helicopters were to conduct an aerial survey and help ground crews with fighting and containing the fire this morning.
The fire started in the area of Alderson Ave, off the Port Hills Rd close to the suburb of Hillsborough, RNZ reported.
It was on the side of the hills facing the city, so Christchurch residents could see it and were phoning Fire and Emergency last night, RNZ reported.
State Highway 76 has been shut off at Curries Rd and motorists are being directed away from the area.
MetService meteorologist Francis Russell said after a few showers early this morning, the forecast in Christchurch was for a fine day with light southerly winds.