A roadside fire, which occurred near a substation and threatened a barley field, is thought to have been caused by a power line fault.
The Masterton fire crew and a Carterton tanker were called to the fire, near the Gladstone substation on the Masterton-Martinborough road, at 1pm on Sunday.
Carterton volunteer fire chief Wayne Robinson said the fire burned about 50 metres of grass on the side of the road and part of a barley field.
"The power line shorted out and set fire to the grass," Mr Robinson said.
"If the wind had been up and the paddock of barley had been a bit drier, it could have been a totally different story."
Property owner David McKay was baling hay when his wife called and said smoke was coming from the field.
"I went to go and get a couple of sacks to wet and whack the fire out with, but then the fire brigade came," he said.
"It went straight through my fence and into my paddock; luckily the barley was green.
"If it had been another three weeks [later] they [the fire brigade] would never have stopped it, it would have burned the whole paddock. It would have caused some serious damage," Mr McKay said.
He feared more fires would occur in the area.
"I'm a bit worried because all the boy racers do skids around here, they're more likely to set the paddock on fire than anything else."
Powerco network operations manager Phil Marsh said the fault had been on a 33,000-volt line. An insulator had failed but he was unsure what the cause was.
"It's very unusual for an insulator to cause a spark. It needs to be a really big spark, usually caused when a car hits a power pole," he said. He suspected the fire may have been caused by something else.
Mr Marsh said the insulator fault had been fixed and further investigations would continue.
"We take these things quite seriously because Wairarapa is quite dry in the summer," he said.