A Brookland Rd resident said she heard a "crack and a smash" before she looked out her window and saw flames billowing from a house next door.
Police and fire are investigating what they are calling a suspicious fire on Brookland Rd at 2.30pm on Sunday in the Western Heights suburb of Rotorua.
No one had been living at the house and no one was hurt in the blaze.
The resident, who didn't want to be named, said she heard the big noise and immediately knew something wasn't right, so looked out her lounge window.