Embers from a burning backyard shed in Thames ignite two other properties after long spell of dry weather.
A man smoking fish in his shed is thought to have started a fire which spread to a house and a factory in Thames.
Fire crews were called to a blaze on Grey St just before 4pm.
They found a shed "well-involved and pretty much destroyed", northern fire communications shift manager Tania Matthews said.
"We're battling three separate fires at the moment, but they're all in the same vicinity - we're not sure of the cause at the moment, though."
One resident understood the fire had started while a neighbour was smoking fish in a backyard shed.
"You could see flames before and a tree and a bit of scrub caught fire too, nearby. The guy got out though."
Ms Matthews said it was initially one fire but embers were thought to have sparked two other fires down the street.
A nearby factory, car parts suppliers Campbell Tube Products, suffered external damage, while a house roof was partly damaged.
Jacqui Hamlet, who works at the Avalon Motel about 500m away, said they could see huge flames at one point.
Crews were also called to two scrub fires in Waikato and Taupo.
The first, in the afternoon, was at the Port Waikato dunes where up to 40 firefighters battled a 7ha blaze after a car burst into flames. The driver fled the scene.
Just before 6pm firefighters were called to a suspicious scrub fire near Chad St and Rainbow Drive, in Taupo. Two separate fires, about 200m apart, at one point threatened a nearby home.
In Masterton, fire also destroyed about $250,000 of equipment in a blaze that erupted while customers browsed at a garden supply business.
GardenBarn owner Laurie Hatchard said the fire broke out in a storage and work shed at the rear of the High St business just after noon yesterday. No one was injured.