Three fire investigators, one specialising in witness interviews, have been tasked with determining the cause of last week's wildfire that ravaged homes and properties on Christchurch's southwest outskirts.
The outcome of their investigation could have serious ramifications if someone is found to be at fault, with the fire expected to cost the region millions of dollars.
The Selwyn District Council will probably try to recover costs from anyone found responsible for starting the fire.
The source of the blaze has been pinpointed to private land behind the Wheatsheaf Quarry in Selwyn Rd.
Council principal rural fire officer Wilson Brown would not be drawn on what caused the fire while the investigation was under way.
A district fire ban started at 12.01am on December 24.
Selwyn Quarries managing director Stewart Callaway said he was not aware of any fires lit in the area during the ban.
Egg farmer Allan Marshall, who is facing a $450,000 bill to restart his business after losing 18,000 laying hens in the blaze, said burning rubbish was common in rural areas unless a fire ban was in place.
"If someone's broken the rules there's going to be some hard questions asked," Marshall said.
Jill Legg, who owns land behind the quarry, said speculation was rife about the cause of the fire, but she did not want to comment until the investigation was complete.
She had not yet spoken to fire investigators, she said.
Brown said a lead investigator and two support staff were working on the inquiry.
The scope of the investigation was threefold - where the fire started, its cause, and interviewing witnesses and homeowners.
While a report on Friday's scrub fire off Thompsons Rd at West Melton was expected by the end of this week, the Selwyn Rd blaze was "far more complex".
"We have to be far more thorough and formal because it has ramifications for people," Brown said.
"It's going to be a very big job."
He expected "some indication" by the end of the month.
A decision on the "next step" would be made after their report was complete.
Fire safety officer Graeme Reid said fires could smoulder for days or weeks, depending on what had been burnt and weather conditions.
Rubbish fires could hold "residual heat", he said, and the risk for the region had not disappeared.
"If we get a couple of nor'west days behind this rain, we'll be back to where we were last week."
FLAMES CHASE QUARRY BOSS
A quarry manager has spoken of flames "chasing" his water tanker faster than he could drive as he retreated from a wildfire he had tried to put out.
Chris Hardwick was first to the scene of Thursday's fire, which started on private land behind the quarry and spread through 150 hectares on the outskirts of Prebbleton.
Hardwick had been working at the back of the Wheatsheaf Quarry on Selwyn Rd when he noticed smoke through some neighbouring trees.
At first he assumed it was under control, as burning off was common in the rural area.
However, the smoke "very rapidly became flame".
"We pretty much knew straight away it was serious."
He got the quarry water tanker, used to suppress dust, and within about five minutes was expelling water on to a neighbour's land threatened by the flames.
However, he was forced to retreat as the fire spread into a hedge and started racing toward Selwyn Rd.
"The way the fire was heading, it would have cut off my exit. I would have been stuck in there," he said.
"I did a U-turn . . . the flames were leaping ahead of me by 10-20 metres at a time. I just got out of there quick.
"It was chasing me down the drive. I wouldn't want to be on foot.
"That's the biggest thing I've ever seen with flames on it."
Hardwick and other quarry workers assisted firefighters for the rest of the day, but he did not consider his attempt to put out the fire heroic.
"We were just mucking in."
Hardwick said the fire destroyed a historic woolshed on the property, about $40,000 of haybales, used as a sound barrier, and about $30,000 of native plants on the quarry frontage.
No machines were damaged.
Hardwick said he was talking to a neighbouring business owner, egg farmer Allan Marshall, about a possible alternative to haybales for the sound barrier.
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