At least two houses and multiple farm buildings have caught fire in South Wairarapa.
Fire and Emergency said it received reports of a house fire on Wards Line in Morison Bush at 3.44am.
On arrival crews found multiple buildings alight, including houses, sheds and barns.
Fire and Emergency is treating the fire as suspicious and said investigators would begin their inquiries as soon as it was safe to do so.
Neighbours said they awoke to flashing lights and flames early this morning.
A woman who lives a few farms away from damaged buildings said she was woken by her horse fussing. She understood three houses and two barns had been in flames.
She was worried about a dog that usually slept in a kennel next to one of the burning barns, but said it was unharmed.
Crews from Wairarapa, Palmerston North and Hutt Valley fought the blazes in a barn, at least two houses and other buildings, Fire and Emergency said. No one was injured.
Police wanted to speak with anyone who was in the area of Wards Line between 2am and 4am, and said officers would be in the local community today as part of the investigation.
Malcolm Coleman, who lives next to the scene, said it was a weird sensation looking out his window and seeing multiple fires.
He said he heard noises outside and peered out to see flames leaping from his neighbour's place.
"Huge shock, woke my wife up immediately. Then I looked over at the paddocks and saw another fire burning and I thought 'what the hell, is it just a pile of trees or is that another fire that's connected?'"
He said the situation had left him feeling quite vulnerable.
Carterton mayor Ron Mark said all the signs pointed to arson.
He said all the buildings were separate, yet caught fire about the same time.
"The report I have is that the fires were started from the outside of the buildings which in itself in suspicious. All the indicators are pointing towards arson of some sort."
Mark said dairy farmers were often out milking at that hour, and rural communities tend to note the unusual.