A data processing blunder silenced a bushfire emergency warning system as multiple life-threatening blazes bore down on homes and people.
The Emergency WA website and app failed about 12.50 pm on Monday during five emergency-level bushfires north and south of Perth in searing heat.
"It's not ideal," Western Australian Premier Roger Cook told reporters on Tuesday.
"It's important that this digital technology is fit for purpose."
The technical difficulties were fixed by about 3.15 pm.
DFES blamed a data processing problem for the outage.
"Alerts and warnings were not impacted on the DFES Facebook page and people could still hear the warnings when they called 13DFES," a spokesman said.
There was also no impact on push notifications being issued and received on the app and key stakeholders, such as media outlets, continued to receive email copies of the warnings.
The department had asked the Emergency WA website and app software provider to take immediate action to ensure it doesn't happen again, the spokesman said.
At the peak of the blazes, which stretched from Warradarge in the Mid-West to Nambeelup, near Mandurah south of Perth, people were told to evacuate, and their lives and homes were under threat.
Those warnings have since been rolled back, with four Watch and Act warnings in place for blazes near Gin Gin, New Norcia and Jurien Bay as of lunchtime on Tuesday (AWST).
There were no reports of property or infrastructure damage, but almost 12,000 homes and businesses remain without power in WA's southern half because of fires.
About 8600 are in the Midwest and Wheatbelt regions, a further 3000 are in the Jurien Bay area, north of Perth, and 450 are in the Augusta area, in the state's southwest.
Meanwhile, power has been restored to more than 104,000 properties, including about 90,000 in the Perth metropolitan area, following a significant storm on Sunday.
At the peak of the storm, about 115,000 customers were affected by outages caused by damaging winds and debris that impacted powerlines and equipment.
