The explosion that ripped a central Auckland house apart in the early hours of this morning has been linked to a gas leak - potentially ignited when an occupant turned on the lights.
At midday fire investigators were only just entering the property, six hours after it exploded into flames.
The man and a woman living inside managed to escape with moderate to serious burns. They have been taken to hospital.
Avondale senior station officer Chris Power told NZME that the investigation is ongoing.
"It appears this has been a gas explosion, possibly from a gas leak," he said. "It's possible the light switch is the source of the ignition.
"The occupants of the house reported that they could smell gas at 4am and at 6am one got up and turned on a light.
"It appears that was the source of the ignition, which caused the explosion."
Power expected fire investigators would finish the inspection this afternoon.
A Vector spokesperson said there was no natural gas in this location.
The house has been levelled after the loud explosion rocked New Windsor just after 6am.
The property was quickly engulfed by flames after a blast residents in neighbouring Blockhouse Bay and New Windsor reported as "like a thunderbolt".
Police say a 42-year-old woman has been taken to Middlemore Hospital with serious burns and a man with moderate injuries has been taken to Auckland Hospital.
Little is left of the house after the massive explosion this morning.
Smoke was left billowing from the site of where the house once stood at the end of a driveway off a New Windsor street in the first few hours after the explosion.
One of the walls could be seen crushed up against neighbouring property a few metres away from where it once stood.
Homes surrounding the property were evacuated as a precaution.
Avondale senior station officer Dave Wood said the explosion blew the roof off the building and the walls collapsed.
"Its totalled," he said.
Wood said the injured couple were lucky to get out alive.
Dramatic footage showed flames consuming the collapsed property.
Blockhouse Bay resident James Wheeler said he was woken about 6am by a massive explosion.
"I got woken up by this almighty bang. It seemed like a thunderbolt had hit my house," he said.
He said the fire, which he could see from the deck of his house, was initially raging and flames and smoke were billowing from a nearby street.
Neighbour Jarrod Darlington who lives barely 20m from the back property said the blast shook his home and for a moment he thought a car had ploughed into his home.
He then heard screaming and rushed out to see a house partially levelled and flames racing through the ruined property.
"You could see the house had split and it looked like the back of it had collapsed."
He said neighbours rushed to the aid of the couple living in the home.
Police said emergency services were called to the house fire just after 6.10am.
Police had set up cordons close to the property.