A liquid accelerant was mostly likely used to start a fire that damaged a historic Mt Eden church hall beyond repair, an investigation has concluded.
The huge blaze broke out in the 133-year-old St James Presbyterian Sunday School Hall on Esplanade Rd on Sunday afternoon, December 30.
A report by Fire and Emergency NZ, released to the Herald on Sunday under the Official Information Act, has classified the fire as "incendiary".
"The cause of this fire is believed to be the deliberate ignition of an accelerant of some kind by a person or persons unknown," the report concludes.
The exact point of origin could not be determined because the building was unsafe for an interior examination.
But the investigator said that "given how fast the fire developed it is most likely that a liquid accelerant has been poured and ignited".
"I cannot see how this fire could have started without human intervention."
The report noted the weather was fine and no lightning strikes were reported. It also ruled out an electrical fire as no utilities were supplied to the building, which was shut down by Auckland Council in 2012 due to safety concerns.
The hall was a known spot for squatters and homeless people and had been vandalised and broken into since its closure.
The fire investigator said police told him a person was reported to have been walking around the site, inside security gates, immediately before the fire.
Detective Sergeant Ewen Settle confirmed the fire had been assigned to a police investigator.
Settle said there were a lot of inquiries still to be made and asked members of the public with information to contact the police and quote file number 181230/7065.
The fire happened shortly after the Environment Court ruled against efforts by the council to prevent demolition on the site, where 18 apartments had been proposed.
The fate of the hall, and the 128-year-old church next to it, became contentious when the Presbyterian Church decided it couldn't afford major renovations and chose to sell.
Developer Andrew Montgomerie agreed to buy it in 2014 and, according to court records, a deal with his entity went unconditional in 2016 but money didn't have to be paid until a consent to demolish the hall was obtained.
The court said the agreed price was $3.5 million. In 2016 the council valued the 2272sq m site and the church and hall at $6m.
Both buildings have a B-grade heritage listing with the Auckland Council.
In its decision on December 14, the Environment Court ruled that demolition could go ahead in the interests of public safety on condition that heritage items were to be salvaged.
The items were to be agreed between the owner and heritage experts from the Civic Trust and the council, but may include roof slate, arched windows and door entrances, timber trusses and tongue and groove sarking and floor boards.
The fire 16 days later made that redundant as the remaining structure was deemed an immediate safety risk and bulldozed soon after.
Presbyterian Church Property Trustees executive officer Kos van Lier confirmed that the church owns the property.
The developer did not settle and the contract was cancelled in April, five years after the initial agreement.
It was no longer possible to save anything, van Lier said. The church's immediate concern was to clear the site and eliminate the safety risk.
The church had accepted a quote for demolition, which would go ahead after Heritage New Zealand had surveyed the site for archaeological interest.
Van Lier said no decision had been made about the future of the property.