Cooler conditions and lighter winds aided fire crews as dawn broke but South Australia state Premier Jay Weatherill said it would be days before the situation was brought under control.

"Even though a significant proportion of the fire perimeter is under control and the conditions were milder overnight many fire fronts are still active within the fire grounds and they'll continue to be battled for some days" he said. The premier late Wednesday said two people had died in the inferno around the town of Pinery about 70km north of Adelaide.

"Obviously we have had the awful news of the tragic death of at least two people and we hold grave fears for many more" Weatherill said. "We can't be entirely sure that we have identified every single person within the fire ground. That work will continue this morning as we carry out a more detailed search of the fire area."

He added that 13 people were in hospital with five in either a critical or serious condition with significant burns. "We know that one of those people has burns to more than 80 per cent of their body. Their condition is being closely monitored. But we do hold grave concerns for them" said Weatherill.

The blaze incinerated at least 16 homes as well as outbuildings farm machinery and vehicles as it raged across a 40km front driven by strong swirling winds late Wednesday he added. Livestock was also lost with reports that 2000 pigs were killed along with up to 150000 chickens.

Country Fire Service chief officer Greg Nettleton said it might still be early in the fire season but the land in South Australia was incredibly dry and only long soaking rain would cut the fire risk. "Until we get really substantial rainfall across the state we're in a dangerous fire situation for the summer" he said.

Bushfires are common in Australia's hotter months with the latest fatalities taking to six the number killed since the annual season began early and in earnest last week when four died in Western Australia including tourists from Britain Norway and Germany.

That blaze sparked by lightning around Esperance 750km southeast of Perth was finally brought under control late Wednesday after tearing through almost 130000 hectares of bushland and farmland. It destroyed two homes and ravaged grain crops.