Australian police said many people remained unaccounted for Monday but no deaths had yet been recorded in fire-ravaged Tasmania state, as large parts of the nation braced for dangerous conditions.
Prime Minister Julia Gillard toured the shaken southern island, where more than 100 homes were razed in catastrophic heat and wind by fast-moving blazes that continued to burn across the state.
Tasmanian police said they had searched 245 properties in the worst-hit areas by Monday morning including 90 badly damaged or destroyed buildings.
"The preliminary screening search has discovered no deceased people at this stage," police said.
Acting Tasmania police commissioner Scott Tilyard added that there had been about 500 missing person's reports following the fires, including from interstate and overseas, with "more serious concerns" for about 100 people.
"That's not to say that there's 100 people that have come to harm, it's just to say that we really need to focus on those people as a priority," Tilyard told reporters.
"Until we've had the opportunity to do all the screening that we need to do ... we can't say for certain that there hasn't been a human life or more than one human life lost as a result of these fires."
Tilyard said it would be a "period of time to come yet" before there was any certainty on fatalities.
Gillard urged Australians to be vigilant in coming days, with scorching temperatures predicted in several states and scores of blazes already burning.
In New South Wales, Australia's most populous state, the mercury was expected to hit near-record levels, with temperatures in Sydney forecast to peak at 43 degrees Celsius (109 Fahrenheit) on Tuesday.
Similar conditions were expected in neighbouring Victoria state, scene of the deadly Black Saturday firestorm that killed 173 people in 2009, Australia's worst natural disaster of modern times.
Some 13 million of Australia's 23 million population live in Victoria and New South Wales.
The prime minister called on those living in danger zones to plan ahead and decide in advance whether they would evacuate or stay and defend their property if fire struck.
"These are extreme events ... we live in a country that is hot and dry and where we sustain very destructive fires," Gillard said.
"This is the time to be vigilant, and I do particularly want to pass that message to the people of New South Wales as the temperature gauge starts to rise."
NSW Rural Fire Service Commissioner Shane Fitzsimmons said the weather would bring the state's worst fire danger for "many, many years", with catastrophic conditions expected in some areas.
"We've got awful conditions coming our way and people need to be prepared," said Fitzsimmons.
Blazes were also already raging in the Australian Capital Territory and Northern Territory and South Australia and Queensland states.
Police said initial investigations of the Tasmania fires suggested that they ignited accidentally as residents who narrowly escaped the fire front described darkness as it approached.
"As the fire came through, what had been a really bright red sky turned absolutely pitch black," survivor Del Delagarno told ABC radio.
Her home was one of just six in the seaside town of Boomer Bay still standing.
"It was if it was the darkest midnight you've ever seen -- it was absolutely horrendous," she added.
Wildfires are a fact of life in the vast but sparsely populated arid continent, particularly in the hot summer months between December and February.
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