A tornado ripped through a busy shopping centre in the north Auckland suburb of Albany this afternoon, leaving a trail of damage and debris.
Weather warnings for Auckland were lifted several hours after the tornado hit but MetService said the bad weather was moving south.
Prime Minister John Key earlier told media he had received advice that two people had died as a result of the tornado, but Waitakere police district commander Gary Davey would confirm only one fatality.
Mr Davey said he believed that number to be accurate.
Mr Key said "it's been a very powerful and quite devastating tornado that's caused a significant amount of damage in a very localised area."
He said that information was patchy, and work was still going on to establish the level of destruction as well as what risks still existed from damaged buildings.
"The MP for Northcote, Minister Jonathan Coleman, is going up this evening and I'll obviously monitor that situation to see what else the Government might be able to do."
Mr Key said he had left a message for Auckland Mayor Len Brown offering Government support.
Most injuries believed to be minor
Witnesses say the body of a man in his thirties was found in the old Placemakers carpark near the shopping centre. Peter told nzherald.co.nz he saw ambulance staff try to resuscitate the man, but they gave up after two minutes.
Mr Davey told NZPA there were several people with moderate injuries, and half a dozen with slight injuries.
He urged residents to keep off the roads and to check on their neighbours.
Tornado causes damage across the harbour
A police helicopter would map the tornado's path. Emergency services said it moved south from the Albany Mega Centre to the Chelsea sugar refinery before heading across the Waitemata Harbour to Pt Chevalier.
Although there have been reports the tornado dissipated over the harbour, some houses in Port Chevalier on the other side of the harbour were also hit by the tornado.
Deborah Hay - who lives on port Chevalier Road - said she was upstairs in her home when she saw a tornado coming up her driveway at about 3.40pm.
"I realised there was something going on because my dog was terrified. Then I heard something coming and I tried to shut all the windows but there was all sorts of stuff flying everywhere.
"Someone else's roof came falling into our yard. I ran downstairs because I thought I shouldn't be upstairs and there was just a wall of leaves and bits of everything outside."
The damage in the area appears confined to Point Chevalier Road and Harbour View Road, right by the water. A bus shelter was smashed by a falling tree, fences in the area have been torn down and some garages heavily damaged.
WeatherWatch.co.nz reports the tornado that ripped through Albany would have had an average wind speed of 200km/hr.
The website's readers have reported cars lifted and thrown, roofs taken off and trees uprooted by the tornado.
Its head weather analyst Philip Duncan says that damage is consistent with wind speeds of between 180 and 200km/hr.
Rumbling kept getting louder and louder
Helena Campbell was working in Pak 'n Save when the tornado hit Albany.
"I heard a loud rumbling which I thought was thunder. It kept getting louder and louder.
"We thought it was an earthquake."
She said when staff and customers ran out into the carpark, they saw debris "everywhere". She then noticed her car was missing. It was soon located in the carpark of the abandoned Placemakers building nearby.
"I'm in a bit of shock, really. It shows the power of [the tornado]."
She said she hoped her insurance would cover "an act of God."
Emergency response underway
The Auckland Council emergency coordination centre has been activated in the wake of the tornado.
Civil Defence said the North Shore Events Centre in Glenfield would be turned into an emergency welfare centre for people displaced from their homes by the tornado.
Work and Income, Victim Support and the Salvation Army would be assisting. Anyone needing assistance should call 0800 463 010.
Earlier this afternoon, at least 15 security guards were standing outside the emergency department at nearby North Shore Hospital.
A Herald reporter at the scene who was prevented from entering the hospital said it looked very busy inside.
Auckland City Hospital spokesman Mark Fenwick said there was a seriously ill 30-year-old male in the hospital's emergency department who was injured during the tornado.
"We've got an incident management team up and running. We're on standby to receive any more [casualties]," he said.
"It's damn real" - eyewitnesses react
North Harbour Rugby commercial manager Richard Turner said he watched as the tornado travelled across the roof of the nearby Westfield shopping centre.
"We were watching debris fly around. One of the girls said: 'that's a car.' We thought 'it can't be a car.'
"You could see pretty big objects, trees and things, circling around."
Mr Turner said the tornado headed off to the motorway and was "so intense it was unbelievable".
He said traffic was banking up and police and ambulance were at the Westfield shopping centre.
Rob Crawford was on the scene when the tornado struck, where what he saw reminded him of the movie Twister.
"Carparks scattered with the remains of trees, upturned cars. There's iron off the roof of the old Placemakers, just wrapped around it ... total mini destruction within the carpark."
"It's surreal. I think, 'it's a movie set. Is this real? Is this happening?' But when you see people lying on the ground, covered in blood, clutching their heads, it's damn real."
Samantha Davey from Albany Optometrists said it appeared that part of the roof at the neighbouring Albany Mega Centre had been torn away.
"We are a bit above the mall, looking down from our building we can see part of the mall roof is gone," she said.
"It looks like it's the bit behind Number 1 shoe Warehouse but our building is a bit above on Corinthian Drive so it's hard to tell.
"There's people at Work and Income, they said they saw a car swept up in it."
Miss Davey said the tornado passed "fairly quickly" but wasn't roaring as it may have been imagined.
One of her colleagues said her in-laws lost a few tiles off their roof in Unsworth.
Kate England was working at the Gordon Harris Art & Graphic Supplies just above the mall when the tornado hit.
"The first 10 seconds I was just in shock. It sounded like a bad car crash."
She said she watched a grey car being lifted 20 feet up in the air near the roundabout by the mall from the window of her work.
"It was the most surreal experience."
"Somebody came into the shop and said the Placemakers building, which the company moved out of about a week ago, is now just a shell."
She said the tornado came from the direction of the Westfield Mall, before moving through the Mega Centre.
Neighbouring area experiences chaos
In nearby Glenfield, Kaipatiki Road has reportedly been closed after a fallen tree blocked the road, adding to the traffic chaos caused by the tornado.
A resident, who did not want to be named, said a "crazy" amount of sirens could be heard in the area.
"I've never heard so many sirens in my life, and the birds have gone crazy. They just flew to the south."
She said the rainfall in Glenfield was "very heavy."
NZ's previous tornadoes
Tornadoes have struck Albany in the past. In 1991 a tornado ripped through the town, destroying a small church and tearing roofs off houses. Wayne Stanley-Hunt died when debris collided with him as he was driving a bulldozer.
There have been several deadly tornadoes in other parts of the country as well.
In August 2004, Rosina Dawn Wikohika, 55, of Levin and her grandson Gary Mason, 10, were killed with a tornado struck the Taranaki town of Motunui, north of Waitara.
On August 25, 1948, a major tornado hit the Hamilton suburb of Frankton, killing three people and damaging or destroying dozens of houses.
New Zealand tornadoes tend to be less deadly than those in other countries. More than 300 people were killed last week in a series of storms and tornadoes in the American South.
- WITH NZHERALD STAFF and NZPA