Firefighters are abandoning efforts to battle the SkyCity blaze from the rooftop, which erupted in the afternoon, and focus on stopping it from spreading further below.
Flames engulfed the top of the building just after 1pm this afternoon - starting on the seventh floor before spreading to the sixth. The cause of the fire is not yet known.
Bitumen and insulation is on fire and there are also concerns about gas cylinders in the area.
Hundreds of people were also evacuated from the precinct, including the Sky Tower, because of the smoke earlier in the afternoon.
Auckland Mayor Phil Goff told Lately this evening that firefighters will abandon efforts on the roof of the Convention Centre but their strategy is to stop the blaze from spreading to the fifth level. At least one helicopter is also circling overhead.
"It's now got to the point where the regional commander has told me that they've abandoned the roof, they think that the roof might collapse so what they might try to do is stop the fire reaching below level five, so I think it's going to be going on through the night."
He said firefighters were also bearing in mind the major crane towering above the building that's also in potential danger of being damaged or toppling over from the fire, but were also confident that their strategy would work.
Fire and Emergency's Thomas Harre said it's been difficult for firefighters to get inside the building and to the top because the fire started in the roof cavity.
The orange glow of flames from the burning centre is clearly visible this evening, and thick black smoke continues to billow from the building.
Fire and Emergency said people may be able to see flames as the crews let some areas burn.
It said this was nothing to be concerned about and was a way to provide access for firefighters to the inside of the building.
Its spokesperson, Dave Woon, said it was "a very, very difficult fire to extinguish".
Mr Goff said there were also hazards battling the blaze from above, in the air, with consideration to the smoke and high rise buildings. But fire crews had extension ladders, and reaching the site with water was not the main problem, he said.
The firefighters have even been able to access the hydrant system within the building, he said.
"But the flammable material is the bitumen under the roofing and below the bitumen they have an insulation and noise suppressant material ... that and the wood and the bitumen makes for a volatile ingredient for the fire spreading, and it certainly has spread, not withstanding the efforts of the firefighters who are doing a valiant job there."
By tomorrow morning the extent of the damage should be more clear but even then it might be too early to know what will it will take to remediate that and the cause of fire, he said.
He said he's been reassured by the regional commander that no-one was injured by the fire but one firefighter fell ill during the incident.
Mr Goff told Lately he saw the fire from the council building where he was at about 1pm and had expected it would be put under control soon.
Firefighters have come off the roof. A sudden flare up that's burning quite strong at the moment. pic.twitter.com/BCt0GJaf7O— Phil Goff (@phil_goff) October 22, 2019
"When you look down on the fire from where our office is, and you know, we saw it expand and it must've been about 80 metres wide at one point.
"But the fire has now spread wide across the roof of the building and you have to imagine that while we're lucky there's nobody missing and nobody injured by the fire - that's the latest report I have - that the damage to property and the impact on the convention centre itself will be quite profound."
The smoke was also having an impact on a wide area of the city centre, he said, and advised people working tomorrow in nearby blocks or those living there to take precautions or avoid the area if possible.
"With the wind blowing from the west and across down Albert Street and beyond, it's pretty unfortunate incident and its rammifications will be quite far-reaching.
"And the atmosphere - where the wind is blowing is pretty acrid, we're not sure whether we'll be able to admit staff to our building tomorrow morning. I was in there until about 7pm and, you know, your eyes are stinging, your nostrils, your throat feel the smell of the smoke, so it's pretty far-reaching.
"The emergency advice has certinaly been it's not healthy to breathe smoke, to avoid the area, and if you're living in the area, turn off your air conditioning, close the doors and close the windows. But even with that strategy in the council building, adjacent to SkyCity, our offices by the end of the day were practically unhabitable, and we sent staff home mid-afternoon."
Niwa said the wind gusts from the afternoon have eased to under 50km/h but are expected to increase after midnight. It said a wind shift is also forecast for tomorrow afternoon, which will result in shift of the smoke plume.
9:30 pm Tuesday: the fire continues at the Sky Tower.— NIWA Weather (@NiwaWeather) October 22, 2019
Wind gusts have eased under 50 km/h, but are expected to increase after midnight.
A wind shift from west to south-southwest is forecast around noon Wednesday, which would result in a shift of the smoke plume. pic.twitter.com/wXckQ3XHAU
The Fire Service has sounded the sixth alarm, which means all available resources from Auckland have been called in, with further resources from Hamilton on the way.
Compartively, the regional commander told Mr Goff that a normal house fire would be level one and a serious big fire level three.
"He [the regional commander] said this is the biggest and complex fire he's had to fight in his career, so that gives you some idea of the scale of the difficulties they're confronting."
Mr Goff said 30 firefighter trucks were on the scene in the evening to battle the blaze, with help from Hamilton being sent in too. He sent out a special thanks to all the firefighters for their efforts throughout the day and overnight as well as Hamilton for pitching in to help.
SkyCity evacuated its entire Auckland precinct, because of smoke from the fire, with people forced to leave the Sky Tower, casino, all SkyCity hotels and restaurants and corporate offices.
The company said police were onsite to help with evacuations.
Mr Goff said while there had been some difficulties in gaining access to the area to transport guests of hotels with their luggage, alternative accommodation for them was being found.
Police and ambulance staff are on the scene to assist fire crews and with evacuations, as well as road diversions.
One man said he was on his lunch break when he thought he heard a fire drill sound out.
"I'm just eating my lunch ... you hear that fire alarm, often before the alarm gets triggered you hear about it before hand and we just left and come here. I just want to finish my lunch."
Apartment fire nearby SkyCity
The fire crews have also had to be pulled away this evening from the SkyCity blaze to fight an apartment fire nearby.
Firefighters were called to the scene on the corner of Albert and Wyndham Streets to see smoke coming from the 15th floor.
Fire and Emergency said the apartment blaze was now out, but it was too early to say what caused it.
Implications on future of construction of SkyCity cenvention centre
Auckland Mayor Phil Goff told Lately that there was torrent of water coming down from the building, and compiled with the fire, he expects there will be significant damages which may put the project back "months or maybe years".
"We don't know yet what implications will be for the ultimate completion of the convention centre and whether it will be ready by the time of APEC."
He said he understood that there were alternative options for Ministry of Foreign Affairs and Trade for APEC if the centre was not to be completed on time.
"Apec is due to be held in November of 2021, and while that sounds like a long way off, with the delays that were already taking place in the completion of the convention centre, and now the fire, you've got to be realistic and assume that an alternative plan B might need to be put in place in the event that the convention centre is not ready."
In a statement, Fletcher Building - the company constructing the convention centre - said its people and contractors were its number one priority at the moment.
Economic Development Minister Phil Twyford said it's a major project with economic benefits for Auckland, so it's a disappointment.
"I'm really happy to hear all the workers have been safely evacuated and it's too early to say with any certainty what this means in terms of construction, but I have no doubt this will be a significant set-back," he said.
MrTwyford said it was unlikely to have any financial implications for the government.
SkyCity's $700 million International Convention Centre and hotel project which has been plagued by problems, including cost over-runs and construction delays.
The casino operator has been hoping the convention centre and hotel complex would be completed by the end of next year in time for the America's Cup in 2021.
The project is set to cost several hundred million more than budget and is running two years late.
It was originally budgeted to cost between $400 million and $500 million, but is now expected to cost more than $800m.
Earlier this year, the company pushed the completion date out to the second half of 2020 - a delay of six months, forcing a review of bookings.
The complex is being built by Fletcher Construction and SkyCity has already triggered penalty clauses in its contract, which require Fletchers to pay damages.
It was expected the convention centre would be ready well in time for 2021, when Auckland hosts APEC and the America's Cup.
SkyCity's share price dropped 2.75 percent today, while Fletcher Building was down 1.5 percent.