Port Hills resident Kieran Grace, who lost his home in February's devastating fires, is part of a group of residents considering legal action after video surfaced that appears to show a burning Christchurch Adventure Park chairlift starting blazes.

A group of Port Hills residents is considering legal action after video surfaced that appears to show a burning Christchurch Adventure Park chairlift starting fires during February's destructive blazes.

It is understood insurers were also considering legal action and had sent letters to some Worsleys Rd property owners requesting lists of uninsured goods destroyed by the fires.

On Monday, police confirmed one of the two Port Hills blazes was suspicious and that a criminal investigation had been launched.

DYLAN HUNTER February's Marleys Hill fire, one of two which ripped across the Port Hills in Christchurch, has been confirmed as suspicious. (File photo)

The Marleys Hill blaze was one of two fires that started on February 13, before joining up and burning through 1645 hectares and destroying or damaging 11 homes. The hill is directly above the adventure park.

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War hero and celebrated pilot Steve Askin, 38, died while fighting the blazes. The Eurocopter AS350-BA he was flying crashed near Sugarloaf on February 14.

ALDEN WILLIAMS/STUFF Kieran Grace, standing in the remnants of his Worsleys Rd home which was destroyed in February's fires, is one of several residents looking at legal action against the Christchurch Adventure Park.

A Fire and Emergency New Zealand (FENZ) investigation into the cause of the fires, which is still being finalised, has found the cause of the Marleys Hill fire was suspicious.

CHAIRLIFT BLAMED FOR SPREADING FLAMES

The adventure park's chairlift was left operating through the first five days of the inferno in an attempt to prevent any one part of the cable being damaged by heat. Most of the chairs, which were largely made of plastic, were badly burned during the fire.

DAVID WALKER/STUFF Some Worsleys Rd residents are claiming a video shows the Adventure Park chairlift spreading fire into the lower parts of the park as it was run to try and prevent hotspots on the cable.

Kieran Grace, who lost his Worselys Rd home in the blaze and was one the residents investigating legal action, wanted to know why the chairlift was left to operate for so long.

He said video footage taken about 2.30pm on February 15 showed new fires starting less than 1 kilometre from his property. His house burned down about 5pm that day.

"Why wasn't it [the chairlift] shut off at some stage, when they knew the fire was in the adventure park?"

IAIN MCGREGOR/STUFF The fire extensively damaged the grounds of the Adventure Park, pictured.

Grace claimed the video showed chairs coming back down the hill and starting "multiple new fires" close to his property's boundaries.

He said the footage "speaks for itself".

"The fire didn't spread through the bike park. These are new fires being ignited at a closer range to populated areas."

SUPPLIED Former SAS soldier Steve Askin was killed in a helicopter crash while fighting the Port Hills blaze.

He believed the cause was the plastic chairs, which he thought had caught fire and "dripped that flaming stuff onto the ground" as they came back down the hill.

"This is just absolutely shocking to see a business that the [Christchurch City] Council is a shareholder in … actively starting new fires during that day, where the fire risk was so big, resources were stretched."

Grace wanted to know why no-one from the fire service or adventure park stopped the chairlift earlier.

MICHAEL HAYWARD/STUFF The Christchurch Adventure Park, which had only been open for a few weeks, suffered significant damage in the fires.

He said he met with the team investigating how authorities responded to the fires in June, who were not aware of the video at that time.

"It was quite concerning that, for that actual operational review, they had no idea that the chairs caught on fire and helped spread the fire."

Grace has been trying to get more information from fire authorities about the management of the fire response, but his requests were rejected to avoid potentially prejudicing the operational review of the response, which was ongoing.

"It's just such a kick in the guts because we've been dealing with trying to move on and everything, but these things just keep popping up and it's just so difficult.

"My mum was in tears last night because she read this letter from our insurer saying they'll be following up with the adventure park over expenses."

A Christchurch Adventure Park spokeswoman said operating the chairlift during fire events was "standard operating procedure as failure of the haul rope would be catastrophic putting lives at risk".

"Health and safety is always at the heart of what we do and this event was no exception."

She said the park had worked closely with the authorities throughout the fires and in the months subsequently.

FENZ director Leigh Deuchars said the review team was aware of the video, which was part of the wider operational review into the fires.

"We understand Christchurch and Selwyn residents affected by the Port Hills fires are anxious to know more information about this review and any recommendations, but we are unable to comment on specific details of the review until it is complete, which is expected in October."

Despite being run throughout the blaze, the 36-tonne chairlift cable was damaged in the fires and needed to be replaced. A new cable was on its way from Austria and was expected to arrive in August.

'HEARTLESS ACTIONS' WON'T CHANGE ANYTHING

Askin's father, Paul Askin, said his granddaughter was "not happy" about the possibility the blaze was caused by "somebody's completely irresponsible, heartless actions".

"If it was arson, people lost their homes, Steve lost his life and that's just such an unbelievably shocking thing to potentially visit on people if you actually deliberately light a fire.

"I would hate to be that person and have that on my conscience."

But knowing the cause of the fire would not change anything for the Askin family.

"We're dealing with the situation that we've got and we're not going to focus on whether it was deliberate or accidental.

"If it was deliberate it's much more of an issue for that person than it is for us."

Detective Inspector Greg Murton said police were seeking new information from the public and wanted to hear from anyone who had "information in regard to the fires if they haven't yet spoken with us".

He said the criminal investigation was "very complex".

"Our investigation is well advanced, evidence gathering and inquires at the scene have been completed and a range of witnesses have been spoken to," Murton said.

"Someone in the community will have information that is crucial to this investigation and we encourage you to make contact with us."

Deuchars said the investigation into the cause of the second fire, in Early Valley, was "still ongoing and expected to take at least a couple of months".

"When a fire is suspicious, it becomes a criminal investigation managed by the police," she said.

"FENZ provides our report and any other information we can to the police for them to carry out a criminal investigation into how the fire was started and by whom.

By February 28, the fire was 99 per cent under control. The blaze was declared officially extinguished on April 20, more than two months after the fires started.

Extinguishing the flames cost rural fire authorities almost $8 million, by far the most expensive wildfire in Canterbury's recent history.

- Audio courtesy of Radio NZ.