A Whanganui house fire may have been caused by children playing with a lighter.
Fire investigators are working to confirm the cause of an Anzac Parade house fire which started in an upstairs bedroom on Thursday evening.
Police believe it was caused by children playing with a lighter on a bed.
A woman had tried to put the fire out with a buckets of water before getting out of the house, Detective Paul Heathcote said.
Four occupants escaped the home uninjured when the blaze started at about 7.30pm.
Four fire crews arrived at the scene to find a bedroom on the second storey well involved.
"There was a bedroom fully involved upstairs," station officer Shane Dudley said.
"It was contained to the top floor.
"Initially we were told there were people inside [but] once we got there we established everyone was out safely."
Mr Dudley said the four occupants were uninjured but some were treated by ambulance staff for minor smoke inhalation.
The fire was brought under control in about 10 minutes while firefighters remained on site for several hours to dampen down the area.
The top storey of the house suffered severe fire damage with water damage to the bottom level.