The 49 victims of the fires were confirmed dead at a dozen locations, Sarah Campbell, a spokeswoman for the police in Victoria, said on Sunday.
A spokesman for the Victoria fire authority also said that 640 houses have been destroyed by the fires.
Dozens of blazes were also raging in New South Wales. Both states have been gripped in a heatwave for the past two weeks.
Fierce winds were fanning the fires and pushing them in unpredictable directions in Victoria on Saturday, as temperatures reached a state record of 47 degrees Celsius.
Forecasters said hot and uncertain weather conditions would continue on Sunday.
Blair Trewin, a climatologist with the National Climate Centre in Melbourne, told Al Jazeera: "They are the most extreme conditions that we have ever seen in historic record in parts of southeastern Australia.
"We are seeing an upward trend in temperatures in Australia as elsewhere in the world."
Australian police said there was no doubt that arsonists were behind some of blazes.
"Some of these fires have started in localities that could only be by hand, it could not be natural causes," Kieran Walshe, the Victoria state police deputy commissioner, said.
At least 20 per cent of the fires in South Australia state were started by arsonists, Mike Rann, the state's premier, said. Another 20 per cent began as the result of "stupidity or negligence".
"These people are terrorists within our nation, they are the enemy within and we have to be increasingly vigilant about them," he said on Sunday.
Victoria's fire authority also said arsonists were relighting fires that had been brought under control on Saturday.
The worst wildfires in recent memory killed 75 people and razed 2,500 homes in Victoria in 1983.