A man whose use of an angle grinder allegedly sparked the devastating Wooroloo bushfire in Perth's northeast has been charged by police.
The breakthrough comes five months after the blaze which burnt through almost 11,000 hectares of bushlands, destroying 86 homes as well as livestock, sheds and machinery.
The 40-year-old has been charged with failing to take due care while in charge of an ignition source and breaching a total fire ban.
He has been refused bail and will face Northbridge Magistrates Court on Saturday.
Police allege the blaze started when the man used an angle grinder to remove a padlock on a sea container located on his Wooroloo property.
"We are not alleging that the fire was deliberately lit," WA Police acting commander Tony Longhorn told reporters on Friday.
"People need to be careful with these catastrophic fire conditions and this is the outcome."
The breach of duty charge carries a maximum penalty of 15 years' imprisonment.
Police say the man was initially interviewed by arson squad detectives on February 3, two days after the fire started.
He was re-interviewed and arrested on Friday after further investigations, including the use of expert reports and weather data to identify the most likely source of ignition.
Acting Commander Longhorn declined to say whether the man had initially misled detectives.
"He provided a version of events - the investigations were ongoing and continued, and I can't comment too much in relation to that because it's before the courts," he said.
It took firefighters five days to contain the massive bushfire, which coincided with a lockdown in Perth and surrounding regions.
A further 195 homes were under threat at one stage but were saved by fire crews.
The cost of joint state government and Commonwealth relief efforts has been put at least $18 million.