Specialist fire investigator Stuart Bootten said no cause had been found as of yet, and it would probably take a few weeks because it looked like things would need to be sent off for testing.
The scene on Petrie St this morning.
He said there was nothing to indicate it was suspicious.
A Northern Fire Communications spokeswoman said it was a well involved house fire that was called in at 8.48am.
Rotorua area prevention manager Inspector Stu Nightingale said the owners had been contacted and would be cutting their holiday in Australia short to come back.
He said the house was being house-sat and it was insured.