A total of 15 fire appliances and water tankers are battling the blaze, which started just after 1pm on a property in Thompsons Rd, near the Waimakariri River.
Three helicopters are also using monsoon buckets to douse flames.
A Fire Service spokesman said the blaze is about 100 metres long but he was unsure whether any homes were in danger or if any evacuations would take place.
"I don't have a lot of information about it at the moment. But we may need more helicopters, we are not sure yet."
Foul play not ruled out
Fire chiefs are not ruling out foul play as they probe the origins of yesterday's (Thursday) Canterbury scrub blaze which destroyed three homes.
The fire which ripped through dry farmland on the southern outskirts of Christchurch, spurred on by strong nor'west winds, was brought under control last night.
Property owners were evacuated from houses, livestock and horses set free, and large cordons put in place as the fire gained momentum.
Helicopters with monsoon buckets and up to 150 volunteer and professional firefighters battled the blaze as it spread across a rural area, popular for lifestyle blocks, between Rolleston and Prebbleton.
The view, while flying over the fire in a chopper while the blaze was at its peak yesterday, was "scary", said Wilson Brown, Selwyn district's principal fire officer: "All you could see were flames jumping everywhere."
He was stunned by its speed.
"This thing was moving extremely fast. You would not be out-running it if you were in front of it."
The intense fire leapt across two roads, before firefighters halted its rampaging 150-hectare advance at Springs Rd early yesterday evening.
The extreme heat of the fire was drying out grass in front of it, until it caught fire, and then it carried on, Mr Brown explained.
Embers could have seen it leap across tarmac and cross roads, or its heat could have made dry areas combust, fire experts said today.
Firefighters have since kept it under control as the cordons were lifted and homeowners returned to see if their properties were still standing.
A fire investigation into how it started has begun.
Shortly before 11am today, nor'west winds picked up, sending nervous glances between fire officials.
Mr Brown was keeping an "open mind" as to the cause of yesterday's fire.
It is believed to have started on private land behind the Selwyn District Court-owned Wheatsheaf Quarry on Selwyn Rd, but the investigation was in its early stages.
Suspicions that it was started deliberately were being looked at, he said.
"To be honest, people can do silly things," said Mr Brown, who believed it was the first major fire in the region since 2003.
Charges could be laid if anyone is found to be responsible for the blaze. They could also be liable for an enormous bill to cover the fire call-outs.
The area was still smoking heavily today, with gusts of wind stirring up flames intermittently, and fire crews were keeping a watchful eye on it.
Pointing to smouldering piles of straw at the boundary to the quarry, Mr Brown said: "These are still active fires."
"Our biggest concern is to try and contain it today by letting it burn out, dampen areas down by hose; basically stopping it from erupting again."
Incident controller Douglas Marshall said he would let the area smoulder and hopefully "burn itself out" without further incident.
Paddocks surrounding the quarry and neighbouring chicken farm, where 18,000 animals were killed in the blaze, are blackened wastelands.
The charring appeared haphazard, with the flames blown in different directions by strong gusts of wind.
The "bizarre" fire patterns were some of the the strangest Mr Brown had ever seen.
Fire officials are on high alert for the weekend, with weather predictions for more hot, blustery conditions.
"It's far from ideal, and we're readying ourselves for another busy few days," Mr Brown said.
