"There are also signs a burglary has taken place."
Mr Chapman said the owners, who have been in Australia on holiday for two weeks, had been told and were due home today.
A family friend said the property was insured.
Mr Chapman said the exact source of the fire was yet to be confirmed.
"Given the proximity of the neighbouring property the danger to life was very real and adds another significant serious element to what has occurred. We need the public's help to find whoever has done this," he said.
Bay of Plenty fire safety officer John Rewi said it was too early to say what was used to start the fire.
Mr Chapman said police were keen to speak to anyone who saw anything suspicious in and around Gloucester Rd, Girven Rd and Bayfair in the 12 hours leading up to the 111 callout.
Information should be given to the police on 577 4300 or the Crimestoppers line anonymously on 0800 555 111.