The blaze broke out during catastrophic fire danger conditions on Wednesday afternoon, and burned uncontrolled in stubble towards the coastal towns of Edithburgh and Coobowie.

Now contained, the fire has charred about 5000 hectares over an area with a 61-kilometre perimeter, wiping out a high number of stock and crops.

At least 11 properties have been damaged or destroyed, including homes and sheds, and 33 people have been treated for minor injuries including smoke inhalation.

The Country Fire Service has confirmed it was started by a power network fault just outside Yorketown.

But, visiting the fire ground on Friday, Mr Marshall said there was potential for the damage to be more serious.

"The fact that there has been no human loss of life is a miracle, because the conditions on Wednesday were catastrophic, right across our state," he said.

"They were possibly the worst we've ever had in the history of South Australia."

Mr Marshall said the local community was returning to scenes of devastation.

"Our heart goes out to them," he said.

David Littleproud, federal minister for natural disaster and emergency management, said those worst-hit by the bushfires could now access payments of up to $700 per family, or $280 per individual adult.

The grants, jointly-funded by the state and Commonwealth governments, are designed to help meet immediate needs including food, clothing and medicine.

"This is to help give dignity to people in hardship because of the fires," he said.

"Further assistance will be made available once we get a clearer picture of damages on the ground."

Those affected can apply for the grants at the relief centre at Stansbury or by contacting the Recovery Hotline on 1800 302 787.

Australian Associated Press