He said:" The roof, involving bitumen, straw and plywood, is compact, and so we are having real difficulty getting into it. "The roof is not safe to go onto, and the floors below are quite a distance below, so actually fighting and putting out the roof fire is very difficult."
The plan was to cool and protect the area from surrounding parts of the building, but let the roof itself burn. "It is the only safe way. It will take a while, 12 hours, maybe more."
Auckland Mayor Phil Goff said the fire was "pretty distressing" and a massive step backwards for the SkyCity Convention Center.
Goff said: "We won't know until there is a full assessment, but I can't imagine this will take anything other than months to repair, construction put on hold and a lot will have to be torn down and started again."
Thick black smoke enveloped parts of the CBD. Emergency services advised downtown workers to stay away from the area.
The fire sent a firefighter to hospital in a serious condition and three more patients were treated by St John staff at the scene.
Every fire crew in Auckland attended the blaze but their efforts to save the building appeared futile.
The delayed centre, due to open next year, was seriously affected by heat, smoke and water.
It started small - there's been speculation a worker left a blowtorch alight while he went on smoko, and the roofing membrane caught fire.
One worker said fire alarms sounded about 1.15pm. At first he assumed it was a drill.
"Then people said, 'Run, run' and we knew we needed to get out."
Hundreds of fluoro-vested workers poured onto Hobson St and Wellesley St, gazing up at the huge plumes of black smoke billowing from the roof. Emergency vehicles began shutting down city streets, as one by one every fire truck in Auckland made its way to the CBD.
From his office, Goff had a bird's-eye view of flames licking west to east across the convention centre's roof. Around 1.30pm he could see a lone firefighter atop the roof but nothing that suggested the fire being brought under control.
Account manager Charli Farman was sitting at her desk when the fire started. She saw a man in an orange construction vest standing atop the building for about four minutes.
"Then he just ran when the flames started to spread."
Within minutes the fire was visible across Auckland, with smoke at times obscuring the entire CBD from viewers on the North Shore. Hundreds of people called 111, watching in horror as the toxic smoke clouds billowed.
Terrifying images from neighbouring skyscrapers captured the full force of the blaze, as firefighters wearing breathing apparatus tried to douse the huge fire from atop an aerial appliance on Hobson St.
At times it looked like the fire was dying down, as the smoke turned from black to white and began to clear. But then it began pouring black from another part of the roof and flames began licking up again, visible from the street.
At 4pm, Fire and Emergency NZ assistant area commander Dave Woon said the fire was not under control and was proving "very very difficult" to extinguish. It had gone to a sixth alarm, requiring resources from outside Auckland in case there was another major event.
Gas cylinders, bitumen and insulation material had been caught up in the fire, turning the smoke increasingly toxic. The smell like burning plastic and chemicals hung in the air across the city.
At the start, large crowds had gathered to watch the fire. But as the street filled with smoke, people started to cough, their throats itching and constricting in the smoke and their eyes stinging. Masks began to come out and people held their shirts up to their mouths.
Emergency workers blocked off the streets, with an ever-widening cordon as the thick smoke continued to pour down. They shouted at curious passersby to move away from the "toxic" and "dangerous" smoke, pointing them further down Wellesley St. But the smoke was pouring east down the street toward Albert Park and filling parts of the CBD.
Surrounding buildings were evacuated, including all SkyCity buildings.
With nearly 2000 commuters unable to reach their cars inside the SkyCity carpark, there were long queues for public transport and confusion reigned as cars and buses were diverted off their normal routes.
Health officials warned of the risks to the elderly and infirm, telling people to stay away from windows and shut off any vents that could draw smoke into buildings. Food prep and cooking areas should be wiped down before use, Auckland Regional Public Health Service warned.
A decontamination centre was set up, with firefighters hosed off as they came away from the scene.
Fire bossesdidn't know how the fire started and it was not their immediate concern.
However, experts have told the Herald the bitumen-based roofing membrane was used on thousands of projects around the country every day and would be unlikely to catch fire.
Industry experts say the fire may have started when a flammable primer, rather than the heat-resistant membrane, ignited.
The membrane is rolled out over the primer and heated up with a naked flame to create an adhesive surface, according to the GM of a company that makes the membrane.
He said it was possible a person laying the membrane could have left the gas torch on near a primed part of the roof and that was what caught fire.
It that was the case, he said the worker would have been highly negligent .
The team involved in installing the waterproofing membrane all escaped safely from the roof.
MPM Waterproofing Services general manager Andrew Pardington said he had a team of up to 12 waterproofers at the convention centre when the blaze broke out.
He said he had a debriefing with them afterwards but would not say what was discussed in regards to how the fire started.
When asked specifically if a worker left a blowtorch on while having a break he said: "From my understanding that's not what happened but there was a whole lot of conversation heard on site, but really it should be left to the investigating team to find out what happened."
Pardington said Health and Safety had been discussed and support offered to his staff during the debrief but they appeared to be ok.
"None of my staff were injured which I was really happy about."
Many workers left their tools, wallets and keys in the building yesterday when the alarms sounded. It's unknown when or if construction workers will be allowed back on site but Pardington is hoping to be able to retrieve equipment as soon as access is granted so he can retrieve equipment.
The inferno could have economic reverberations for the hundreds of construction workers, tradies and sub-contractors working on the development.
There has already been talk about workers losing their jobs if the building is too badly damaged .
Harbour Asset Management portfolio manager Shane Solly told the Herald the blaze was a further set back for both Fletcher Building and SkyCity, that could have a bigger impact on Auckland's economy.
"[The convention centre] was on the cusp of providing some important stimulus - providing a facility that would have provided some good growth for the Auckland CBD and for the wider region, so any setback is not great."
In February this year, SkyCity confirmed that construction delays had further pushed back the opening date for the convention centre.
The delays were understood to impact as many as 8000 delegates who had booked events early in 2020.
SkyCity said that the venue was scheduled to open in the latter half of next year.
At this stage, it is still unclear whether the devastating fire will push that date back further.
SkyCity's share price plunged as news of the fire broke, dropping from $3.98 to as low as $3.82 before closing the night at $3.87.
APEC is due to be held at the centre in 2021. But the Prime Minister said last night it was too early to say what impact the fire would have on New Zealand's hosting of the international event.