A tornado ripped through the Auckland suburbs of Avondale and Te Atatu on Sunday afternoon, downing power lines and damaging up to a dozen homes.
It occurred about 1pm after heavy rain and strong winds had battered the Auckland region.
Fire Service northern communications centre shift manager Jaron Phillips said the damage in the Wairau Avenue area of Avondale is about 1km wide but there had been no reports of injuries.
A number of power lines were down across the houses. Some caught fire, and a house in Ash Street was struck by lightning.
Mr Phillips says roofing tiles are off several properties in Wairau Avenue, which appears to be the worst affected street.
Wairau Avenue was closed on Sunday afternoon.
Radio New Zealand's reporter in Auckland said there were large chunks of corrugated iron on footpaths all around Wairau Avenue and Canal Road after being torn from sheds and roofs during the tornado.
She said power was still off in the area at 5pm on Sunday after the lines burst into flames causing a few trees to catch on fire.
The tornado then moved north east, across the Whau creek to Te Atatu South where it damaged at least three properties in Jaemont Avenue and Merchant Avenue.