Police are seeking help from the public after an unexplained fire in Masterton on Saturday evening.
Detective Sergeant Matt Wasson said a fire investigator had so far been unable to determine the cause of a blaze that damaged the back of a house in Millard Ave.
Fire services were called out to the fire at 5.24pm, and spent more than an hour at the scene.
Mr Wasson said anyone who may have seen something suspicious in the area at the time should call Masterton police, or Crimestoppers.
The owners were away from the house at the time and Mr Wasson said someone may have noticed "someone who shouldn't be there", or anything else of interest.
"Any fire we do treat as serious and we want to know what the cause is."
Three fire appliances attended the blaze which was first spotted -- and tackled -- by neighbours Terry Phelvin and Kath Cox, who are building a house on the site next door.
The couple were returning from the Wairarapa Wines Harvest Festival to their home in Upper Plain, and stopped at their section to plan yesterday's gardening jobs.
"Kath saw some smoke and said 'why have these dumb people got a fire going?" Mr Phelvin said.
"I went over there to tell them to put the fire out because there's a fire ban."
Mr Phelvin then saw flames which were burning in the flax plants beside the house and the wall of the house itself.
The couple called the fire service and at the same time rushed to use their garden hose to try to douse the flames, which were in the flax and up the side of the house.
"They're lucky we had the water on and a double length hose so we can water our plants," Ms Cox said.
"There was him yelling at me to pull the hose and them saying we can't hear you, you're breaking up.
"At the time it was a bit of drama. We weren't quite sure if the dogs were inside."
Mr Phelvin said his hose "helped some, but not a great deal" to slow the fire, but the fire service arrived within five minutes of the call and relieved him.