Smoke was the only warning sign for a family of six that a fire had broken out in their rural Merriwa home in the early hours of Wednesday morning.
Four fire crews from the RFS and Fire & Rescue were called to the four bedroom home off Idaville Road just after 3.30am and could not initially trace the smoke billowing from the rear of the house to any open flames.
Two adults and four children evacuated themselves safely, although at least two of them were treated on site by paramedics for smoke inhalation.
Firefighters eventually located a small fire which had broken out inside a wall cavity, and had to remove the lining from the wall and roof to stop it from spreading to the rest of the house.
The flames were extinguished within a hour, but crews remained on the scene until just after 8am to carry out a sweep of the rest of the residence.
The Rural Fire Service says the cause of the blaze is still a mystery, with initial investigations ruling out an electrical fault as there was no wiring located in the wall.
It is not being treated as suspicious.