Three adults and a child were taken to Thames hospital after a house fire in Waihī.
Three of them suffered moderate injuries and one a minor injury related to smoke inhalation.
A Waihī Fire and Emergency crew was called, soon after midnight, to the fire soon at the corner of Tauranga Rd and Adams St, near the southern entrance to town.
Two fire engines were sent to the scene and the blaze was well under way on their arrival.
"The house was burnt to the ground when we got here," senior officer and acting chief John Harris said.
The occupants evacuated the house before the fire brigade's arrival.
A fire investigator is investigating.
"We have an idea to where the fire started but have to work through it," Detective Simon Everson of Waihī CIB said.