Some neighbours were also asked to evacuate because a gas bottle attached to the side of the Tay St home had started to vent from the heat.
A section of roof at the back of the older-style wooden home appears to have partially collapsed and smoke damage can be seen around the windows and door of the house.
Today police were on site and a crime scene has been declared but a QPS spokesman said there was nothing to suggest the fire was suspicious.
A police crew remains outside a Tay Street home following a fire overnight in South Mackay.