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 a scrub fire 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.