Fire destroyed a farm house at Maxwell near Whanganui during the early hours of Sunday morning.
It is believed that firearms at the property were stolen before the fire was lit.
Owner Ryan Goble, who was asleep in another house on the property, said passersby stopped and alerted him at around 1am.
"When I looked out the walls were well ablaze and when I got down there the roof had collapsed," he said.
Mr Gable said there were guns kept inside a locked cabinet in the house and there was no sign of barrels among the ashes after the fire brigade had extinguished the fire.
The farm worker who lives in the house was away for the weekend.