By Kathryn Westcott
Australia's prime minister has referred to them as "mass murderers", another senior official has described them as the "enemy within". Who are the arsonists believed to have started some of the fires that have killed more than 130 people?
Australia has a long history of "bushfire arson". According to a recent report by the Australian Institute of Criminology (AIC), an estimated 50% of the nation's annual 20,000 to 30,000 bushfires are either known or suspected to have been deliberately lit.
Investigators say a number of fires were deliberately started
But little is known about the arsonists.
Police in Australia's southern Victoria believe arsonists started some of the fires that have killed more than 130 people, and investigations have started to try to track down the perpetrators. But, similar cases in Australia and the US indicate that it could be a long and frustrating process.
Apart from the fact that an experienced bushfire arsonist is an elusive culprit, much of the crime scene evidence is immediately destroyed or is altered significantly.
According to the AIC report, only a small proportion of arsonists are ever caught.
"It's a huge field which has been inadequately researched," says Adam Brett, a forensic psychiatrist in Western Australia, who has specialist knowledge of the arson.
"All fires start with a small fire and the consequences are not always anticipated," says Dr Brett.
Very little is known about the motives behind bushfire arson
"There are subtypes of people who light fires, from people covering up crimes, to people who are expressing their pain to people who light fires due to mental illness. There are very few people who light fires for the fun of it.
"Then there is a group of hero firefighters - people who light fires so they can put them out."
Rebekah Doley, a clinical psychologist at Bond University in Queensland, says we probably know more about the "dumb arsonists" than the "smart ones", who are rarely caught.
Ms Doley, who has researched the crime of arson and interviewed a number of culprits, says arsonists are unlikely to be pyromaniacs. The term pyromaniac, she says, implies they are unable to help themselves, while arsonists choose to light fires for a number of reasons.
She says that the characteristics of urban arsonists and bushfire arsonists differ. Urban arsonists, she says, tend to be motivated by things like revenge or financial reward, such as insurance fraud. Bushfire arsonists tend to be motivated by psychological needs such as a quest for power or excitement.
"These individuals tend to be underachievers in terms of education, they are not part of the community and are loners. Starting a fire gives them control over their environment," she says.
Reports at the weekend suggested that some of the fires had been deliberately relit after they had been put out by firefighters.
"As the police cordon closes in around them, they might light more fires to seize control back, and to prove that they are smarter than the authorities," says Ms Doley.
Then there is "thrill" aspect of the crime. Arsonists often return to or hang around the scene of the crime, to watch firefighters and emergency services respond.
Forensic teams face an unprecedented task
It is not unknown for several arsonists to work separately at the same time.
A number of unrelated arsonists were responsible for the devastating "Ash Wednesday" fires in 1983, in which 47 people were killed, 2,800 homes destroyed and 210,000 hectares burnt.
However, Ms Doley says, this is not typical.
"Bushfire arson is a very opportunistic crime - a somewhat impulsive one, in which people tend to work alone" says Ms Doley, while acknowledging that some arsonists may be inspired by media coverage to commit copycat crimes.
She says they are unlikely to ever feel remorse for causing damage or for any resulting loss of life because they feel so disenfranchised from their community.
Sometimes bushfire arsonists sign up as volunteer firefighters. This has prompted the fire services to establish screening mechanisms, which work to a "greater of lesser extent," according to Ms Doley.
Australian authorities say they will relentlessly hunt down those who sparked the most recent fires. But previous cases indicate investigations could be either lengthy or fruitless.
"Bushfires are harder to catch, domestic fires are easier because investigators may, for example, find accelerants near the scene," says Dr Brett. "If the bushfire arsonists get caught it's usually at the site by an eyewitness."
Ms Dole says few arsonists are convicted of starting the actual fire because the burden of proof is so difficult in such cases, . "Fire setting is hidden among the other offences," she says.
She says that given that arson is such a perennial problem, greater co-operation is needed between the nation's various local and state agencies to tackle it properly, including the setting up of a national database.
According to the AIC report, between 2001 and 2005, 276 people were convicted of arson in Victoria, but for the third who did go to jail the most common sentence was one year.
Such a sentence may seem inadequate to Australians faced with the devastation and loss of life caused by the latest fires.
One state premier has gone so far as to call those responsible "terrorists".