Metropolitan Fire Service (MFS) is treating the two incidences as separate and fire experts from Adelaide are investigating the second blaze with police.

South Australia MFS regional manager west coast Darryl Horsell said the first fire was attended at about 10.30am on Saturday.

He said it was a small fire in a clothes dryer in the laundry of the house.

Mr Horsell said firefighters removed the clothes dryer and vented the premises to remove the smoke and two residents were treated by ambulance officers on the scene.

He said about three hours later firefighters returned to the same address following several calls.

"On arrival the house was well involved with flames coming from the two bedrooms at the rear of the house and the fire spreading rapidly throughout the remainder of the interior and towards the adjoining house," Mr Horsell said.

"The fire quickly grabbed hold in the roof space and firefighters were forced to put a defensive operation into place.

"Crews working inside the house with breathing apparatus were withdrawn due to the danger of roof collapse and concentrated their efforts to gain access to the fire in the roof area by removing sheets of iron roofing from outside.

"Due to the very oppressive weather conditions and the type of firefighting required, the South Australia Ambulance Service paramedics attended to keep the firefighters hydrated and to monitor their condition.

"Crews were rotated between work and rest and the fire brought under control at 4pm."

Mr Horsell said a smoke alarm was fitted but the battery had been removed making it inoperable.

He said substantial damage was caused to both dwellings.

Mr Horsell said fire cause investigators travelled from Adelaide to investigate the cause and said police are also investigating.

"The first fire was in the laundry and slight damage was caused to a clothes dryer," Mr Horsell said.

"There was no spread of fire from the clothes dryer.

"When the crews arrived for the second fire the clothes dryer was still outside and not involved.

"The second fire started in a bedroom well away from the laundry.

"Fire cause investigators who travelled from Adelaide have determined the two fires were not linked."