This afternoon, the Fire Service said the cause of the fire was not yet known.
A fire investigation team were still working at the scene, Steve Callagher, duty officer at Henderson Fire Station, said.
"Fire investigators are still on site, sifting through the burnt remains trying to establish a cause," he said.
A spokesman for Auckland Council said it was too early to say what had sparked the blaze.
Filming of an international production on the site was proceeding with 300 staff despite the fire, Auckland Council said in a statement.
"The current production is concentrated in the major purpose built sound stage which was unaffected by the fire. The other facilities have not been affected. This production and the ones that follow can be confident it is business as usual."
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Auckland Film Studios chairman James Hill said they were extremely thankful damage caused by the fire was limited and that production on site can continue. "Our thanks go out to the fire service."
The studio is one of the largest in the country and has previously hosted productions including Mr Pip, The Chronicles of Narnia, Whale Rider and the Xena series.
George Schneider, owner of neighbouring European car restoration business Europro, said he had been staying late at work when the fire broke out.
"I was just about to go home when I was alerted to the fire engines, I thought 'holy hell, what's going on here'."
Mr Schneider said he initially dismissed the sound of the sirens as there is a fire station nearby, "but it wouldn't stop, so I went outside".
He then saw the extent of the out of control fire with leaping flames and "huge columns of smoke".
"What set it off, I don't know."
He said he was concerned about the classic late 1950s Porsche 356s he had been restoring.
"I've got $200,000 worth of cars here - just those three cars alone.
"I was making sure that this wouldn't escalate. I could have got them out - at least all three of them roll. Luckily the wind was a bit sou'west so it wouldn't really [spread towards my workshop]."
Mr Schneider said he stayed at the site until the fire began to die down around 1.30am.
"It took them a while."