Hundreds of firefighters, including strike teams from Victoria, will work for the next two to three days to contain the major bushfire burning north of Adelaide.
The blaze has destroyed 85,000 hectares of grass, cropping land and scrub and still has the potential to break out of its existing perimeter, the Country Fire Service says.
Efforts on Thursday will focus on securing that 210km perimeter along with safe access to the fire zone to allow some residents to return to their properties and for essential services, including power supplies, to be restored.
"Our priority from today onwards is to secure the perimeter as quickly as possible and then to add depth to that security over time," CFS chief officer Greg Nettleton said.
"We'll have the Victorian crews starting work tomorrow morning and they'll work alongside South Australian crews throughout the weekend.
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"We're hoping to have the fire declared contained in the next two to three days but we'll only do that when we're sure there's no prospect of breakaways."
Two people have been killed in the blaze and 13 people are in hospital with five of those in a serious or critical condition.
At least 16 homes have been destroyed along with outbuildings, vehicles and farm machinery.
A watch and act message remains in force with the CFS warning the blaze is still 'a going fire'.
Fire activity remains around many townships including Owen, Hamley Bridge, Tarlee, Freeling, Wasleys, Kapunda and Greenock.
Smoke in the area may also impact on visibility and there remains the potential for structures to be impacted, the CFS says.
Weather conditions across the fire ground zone are more favourable with lower temperatures and higher humidity.
But winds of 25-35km/h are a concern.
