The residents, two men aged 65 and 30 and a 65-year-old woman, escaped the property safely.
A number of nearby homes were evacuated by police as a precaution while the Northern Ireland Fire and Rescue Service dealt with the blaze.
Detective Constable Colin Robinson said: "We are keen to hear from anyone with information about this crime or from anyone who may have been in the area at around 5.30am this morning . The number to call is 101.”
Meanwhile, detectives in Bangor are investigating a deliberate fire in Kearney Gardens.
The front door of a house was set alight between 9pm on 31 March and 1am on 1 April.
The male resident was not home at the time.
Detective Constable Ryan Armstrong is appealing for witnesses or anyone with information to contact the offices of Reactive and Organised Crime at Bangor Police station on 101.