• Fire boss says fire 'still smouldering' on convention centre roof
• Firefighters are 'fatigued', while centre basement carpark is 'underwater'
• The centre roof has now partially collapsed
• Exclusive: First photo from inside SkyCity reveals devastation
• SkyCity fire: 'Work from home', what you need to know for today's commute
• Two fires and a wedding: How SkyCity blaze upended couple's big day
The fire at the Sky City Convention Centre has reignited, with flames visible again on the roof.
Thick black smoke has swamped surrounding streets, in a blow for firefighters who believed they had the "smouldering" area under control.
The smoke filled Hobson St just before 2pm and minutes later the flames could be seen.
Fire and Emergency area commander Richard Twomey said at a news conference that fire crews have been using drones to look for hotspots.
"It's smouldering,'' he said. "We're in a better place than yesterday''.
Twomey confirmed there are 400 total cars in the parking building. They can't say for sure how many vehicles are in the lowest basement, but said the water was up to the windows.
The inferno at SkyCity's new convention centre that sent a haze of smoke over Auckland and closed major roads was overnight coming under control but its effects are expected to be felt well into the future.
At its peak, 150 firefighters and 30 fire appliances battled the blaze in the $700 million convention centre, which was still under construction.
Firefighters kept up a constant torrent of water on Wednesday and by afternoon, Fire and Emergency said the blaze had been contained to the convention centre's sixth and seventh floors.
Small bursts of flames could be seen on the building's roof at 9pm, but fire officers said it was slowing down. They expect to be at the site for days.
"We are without any doubt winning the battle against the fire," said regional manager Ron Devlin said this afternoon.
The construction site made it one of the most challenging fires tackled in recent memory, but letting the roof burn out was proving successful, he said.
Nearly all businesses around the scene of the fire closed yesterday and more disruption is expected today.
Auckland Council, the Auckland District Court, the Central Library and the City Art Gallery also shut their doors for the day.
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SkyCity said its casino, both hotels, the Sky Tower and all its restaurants remained closed yesterday.
Motorists were advised to avoid the central city again this morning, as parts of Hobson, Nelson and Wellesley Sts will be closed.
Those who could work from home or non-central locations were advised to do so.
"If you are able to time your travel to avoid peak-hour traffic, by leaving earlier or later than usual, we advise you to do so," said John Nottage of AT.
Train services were not affected but some bus routes had been altered.
Auckland Regional Public Health Service advised people to take precautions because of lingering smoke affecting air quality across the CBD.
One firefighter was taken to hospital yesterday with moderate injuries after being struck by a piece of falling roof and suffering a concussion.
"It was unusual, and may have been flicked off in the wind," Devlin said. "It is not what we want to happen, and [why] we have been very careful with internal operations."
St John confirmed to the Herald a further five people were treated at the scene for minor injuries.
Prime Minister Jacinda Ardern, who visited the site yesterday, said she wanted to acknowledge the firefighters who had been working under difficult circumstances.
"The team on the ground have been incredibly professional, very focused on what they can do to preserve the building."
Aucklanders went out of their way to help with pizza and sushi donated to the crews, and one man drove up to the cordon, dropped off a tray of bottled water and shook a firefighter's hand before driving off.
Viaduct restaurant and pub HeadQuarters offered firefighters free meals, drinks and a place to lie down.
"Don't even ring, just turn up. We know you, you know us, you're gold, and we owe you this."
Janelle Himmel arrived at the cordon to check in with her fiance, Daniel Rosan, one of the many firefighters battling the blaze.
"Seeing this makes his job very real," she said.
The couple, who get married next month, shared a kiss and spoke briefly at the cordon before Rosan had to leave again.
Although the fire had affected the sixth and seventh floors, Devlin said the fifth floor looked in good shape. The roof's membrane was damaged, but the structure looked to be intact.
"We expected the roof to burn and collapse, and it is doing exactly that."
Once the roof had burned through they could enter the building and tackle the fire internally.
SkyCity chief executive Graeme Stephens said he hoped staff working on the convention centre project would be back at work tomorrow.
Stephens and Fletcher Building chief executive Ross Taylor were adamant that the centre would eventually open, although no timeframes could now be given.
"It was an amazingly iconic building yesterday and will be again.
"We will get the phoenix out of the ashes," Stephens said.
Taylor backed him up: "This is a very important project for SkyCity, Auckland and New Zealand and we will get this project finished to quality and make sure it's the iconic building and a very important piece of infrastructure Auckland and New Zealand needs. Fletcher is committed to getting the project finished and we will."
Ardern said Apec 2021 would still be held in Auckland, but the venue was a point of discussion for Government.
"New Zealand has hosted Apec before ... without a convention centre. We had contingency in place."
Officials refused to speculate on how the fire started, but workers said they believed an unattended blowtorch could have ignited the straw-like acoustic layer, quickly spreading to the roof's bitumen membrane.
Fire and Emergency was also working hard to ensure any run-off from water used to fight the fire was minimised, and Auckland Council and Watercare were monitoring this as the emergency continued.