The banking sector has had to reassess security at Perth automatic teller machines after 15 explosive attacks in two months.
Criminals have been using a volatile mix of gas and petrol to try to blow up the cash safes but have even doused one or two with petrol and ignited them.
The blasts have left a trail of destruction at the ATM sites but have rarely netted a pay day. Thieves got to the cash on just two of the 15 attempts.
However, for just a few minutes risky work, the crime can be lucrative, with cash machines reportedly able to store up to $500,000.
A police task force has been set up to track down those responsible for the latest raids, which started in October at High Wycombe and ended with explosions at ATMs at two shopping centres within minutes of each other on December 28.
Detectives from the regional investigations unit, arson squad and suburban offices, with support from forensic experts and bomb squad officers, are running the investigation, codenamed Operation Boiler.
The banking industry is offering a $50,000 reward for information leading to the arrest and conviction of the criminals, saying as well as damaging the machines, the attacks endanger passers-by.
Acting Det-Insp. Jason Fogliani said it was highly likely that the same people were responsible for more than one of the 15 attacks, but not all were linked.
Police say the latest incidents appeared to be "copycat" attacks of heists in July and August 2012.
Australian Bankers Association chief executive Steven Munchenberg said the banking sector was working with police, assessing risks at WA's network of 3050 cash machines and upgrading security.
"Individual banks take different approaches according to the types of ATMs in their fleet, where they are located, the infrastructure which surrounds the machine, visibility and lighting, and the security history of the site," Mr Munchenberg said.
"Installation of gas detection and suppression systems and toughening physical security on ATMs are some of the measures which banks use."
It is believed less cash is being put in some machines and they are instead being filled more frequently to limit potential losses.
Cash machines also have been targeted in explosive attacks in other States.
Acting Det-Insp. Fogliani said the recent explosions had significantly damaged businesses surrounding the machines, with some having to close temporarily for repairs.
"These methods are rarely successful but are always dangerous to the offenders, the emergency services who respond to the explosions, to other people who work in the vicinity and members of the community," he said.
"The reality is someone could be seriously injured or killed if they were in the wrong place at the wrong time."
Anyone with information is asked to call Crime Stoppers on 1800 333 000.