Falling tree sparked deadly SA bushfire

A tree falling on power lines is thought to have sparked the devastating bushfire in the Adelaide Hills which has claimed at least one life and caused potentially millions of dollars damage.

As the blaze continued to burn out of control on Saturday, damage assessment was underway, with 15 homes confirmed as destroyed so far along 28 other buildings and 16 cars.

Live updates: the bushfire crisis

There were also significant stock and crop losses including vineyards.

Authorities said 23 firefighters and two police were injured, some through smoke inhalation, and three fire trucks had been destroyed in a burnover.

One person was found dead at Charleston with police checking a number of other properties to ensure no further loss of life.

That death came after a motorist hit a tree and was killed in the state's southeast on Friday, causing a stubble fire there.

Another 29 people were taken to hospital with at least one of those in a serious condition with severe burns.

The Adelaide Hills fire had burnt through more than 25,000 hectares of scrub by early Saturday with 40,000 hectares destroyed across SA as more than 100 fires raged amid catastrophic conditions.

At one stage 1200 firefighters and more than 400 fire trucks were in the field.

Premier Steven Marshall said he believed the damage bill could go higher as people were allowed back into properties.

"My fear is this is only the tip of the iceberg," he said.

"It is going to be a real scene of devastation, especially for those people in the Adelaide Hills who have been most affected."

Police Commissioner Grant Stevens said a task force would examine the circumstances surrounding the fire, the level of damage it caused and what led to the death at Charleston.

But he said preliminary inquiries suggested a tree falling on power lines as the cause.

Road closures were also being reviewed to determine when property owners would be allowed to return.

In pictures: The summer of devastating bushfires

A watch and act warning remained for the fire on Saturday with the towns of Cudlee Creek, Gumeracha, Lobethal, Woodside, Mount Torrens and Harrogate of most concern as it continued to burn northeast.

Country Fire Service chief Mark Jones said firefighters would work to protect assets and contain the blaze.

The weather would not be as bad leading up to Christmas but there was still potential for fires to escalate.

Mr Jones said crews would remain vigilant to ensure the continued safety of the public and emergency workers.

"Against the catastrophic conditions and the backdrop of unprecedented challenge, it's remarkable that so few of the firefighters and emergency responders were injured," he said.

"But obviously there is a lot to do in the coming days and the coming weeks."

In other parts of SA, a watch and act message remained for a blaze burning across the north coast of Kangaroo Island constantly affected by high winds and varied terrain.

Most other fires across the state remain downgraded, including one at Angle Vale, in Adelaide's north, which also caused some property damage.