Fletcher Building has confirmed there were no automatic fire alarms installed on the incomplete levels of the SkyCity Convention Centre - which is burning into its second day - and the blaze was spotted by a supervisor.
The company's boss Ross Taylor and SkyCity's chief executive Graeme Stephens fronted media this morning at a press conference in Auckland, just blocks from the raging fire.
Taylor also said blowtorches were being used on bitumen to seal joints at the site and that is where he believes the fire started.
He said the convention centre remained an iconic piece of infrastructure and Fletcher Building was "committed" to ensuring it was completed.
Stephens thanked front line emergency services staff and acknowledged their "immense efforts" in fighting the fire.
He said SkyCity had a crisis management plan that he hoped he would never have to activate.
But to see his staff pitching in and the plan being implemented was heartening.
He said the evacuation process was started early and included finding alternative accommodation. He did so to ensure it did not become a crisis situation and the evacuation could be done over hours.
"Very thankfully we are not dealing with human loss," he said.
"This is a discussion around buildings and money and time - but not people."
Stephens acknowledged SkyCity customers and said the hotel, restaurants and conference areas were all full when the evacuation began.
"Hopefully we can make it up to them."
Stephens was confident the project could be rebuilt and open in the future.
"Fletchers is committed to getting the project finished, and we will."
He said there was no alarm system on an active construction site - and the fire was spotted and reported by a supervisor. He said protocols were in place and worked well. It took just 20 minutes to evacuate the site.
Fletcher Building later clarified that there were active alarm systems on all completed floors.
"It was on the floors still under construction where there were only manual alarm systems," a spokeswoman said.
A full assessment would need to be done when the fire was out, and there was bound to be significant water damage which also had to be factored in.
He could not quantify how long it would take to start the rebuild.