At least eight homes and thousands of hectares of land in Victoria, South Australia, Tasmania and Western Australia, adding to around 20 buildings already destroyed in Victoria.
Despite cooler temperatures and lower winds, fire authorities warn that the fires could intensify later in the week, when temperatures are expected to top 40 degrees Celsius.
The bodies of an adult and a child were found inside a crashed car around 220 kilometres west of Melbourne, and police said it appears the pair died as fire swept over them.
"It appears the car... ran off the road, the fire may well have overtaken the car," said local District Inspector Martin Dorman.
In a separate incident, Victorian police said a firefighter died when his truck overturned while tackling a blaze in the state's northeast.
Farmers in Victoria say they expect tens of thousands of cattle and sheep killed by the fire, with many more having to be culled after sustaining injuries in the blaze.
The fires in SA and Tasmania are not yet threatening property, however residents of the town of Dwellingup, 100km outside Perth, have been warned to be vigilant, with a nearby fire expected to double in size.
Earlier, Victoria Country Fire Authority Deputy Chief Officer Graham Fountain with daybreak, authorities were able to assess the extent of the property loss at daybreak.
Speaking to Sky News, he also said police and fire crews faced a slow search through vast burnt out areas in the Grampian mountains.
"We've got well in excess of 100,000 hectares of burnt area with very active fires and hazardous terrain," Mr Fountain said.
The fire in the Gippsland has been burning towards the towns of Moondarra, Erica, Tyers and Rawson.
In south-east SA, fire crews battled a large blaze at the Ngarkat Conservation Park, which has burnt an estimated 60,000 hectares.
At least seven houses also came under threat as bushfires swept across Kangaroo Island.
Hot winds in Tasmania, fanned a blaze at Trial Harbour, near Zeehan in the state's west.
The fire destroyed nearly 3,000 hectares of bush and scrub but cooler conditions helped crews bring the situation under control.
In Western Australia, a large bushfire continues to burn out of control near the south-west town of Dwellingup.
According to ABC radio, it’s believed the fire may have been deliberately lit in a blue-gum plantation.
Department of Conservation and Land Management spokesman Roger Armstrong has told the ABC it would be crucial to contain the blaze on Monday ahead of thunderstorms forecast for Tuesday.
"One of the other things that's confounding us a little is the impact of tropical cyclone Daryl as it decays and moves south," he said.