Police in Australia believe that arsonists were to blame for some of the fires which have caused destruction in the south-east of the country.
Almost 30 homes were destroyed in the Gippsland region of Victoria, after the state experienced its worst heatwave in 100 years.
Meanwhile, a new report suggested that half of the country's bush fires each year were started deliberately.
The Gippsland bush fires have been made worse by high winds and low humidity.
But the police believe at least two of them were started by what they described as a serial arsonist.
The launch of the investigation coincided with a new report from the Australian Institute of Criminology which found that half of the country's 20,000 to 30,000 wild fires each year were started deliberately.
It said arson cost the country over $1bn each year (£694m), and that only the crimes of drug dealing, fraud, and burglary did more economic harm.
The report said there was a strong link between arson and other forms of criminal behaviour.
It also found that arsonists are often attracted to careers in the fire service, or volunteer to help fight fires.
One explanation is that they get a thrill out of trying to combat the blazes.
Last November, police in New South Wales charged a volunteer firefighter with 13 counts of arson.
A record-breaking heatwave in south-eastern Australia has left firefighters struggling to contain the bush fires.
But meteorologists say that the mercury is set to dip below 40C (104F) for the first time in days.
Health officials report more than 20 heat-related deaths, mainly among elderly people.
Over the weekend, saving properties has perhaps been less of an urgent priority than keeping the fire away from a major electricity transmission line that serves Melbourne, Australia's second most-populous city.
A surge in demand for air conditioning has led to power cuts and rolling black-outs.
Traffic lights have ceased working in parts of the city. On the trains, buckled rail lines have led to widespread cancellations.
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