The blaze at Wooroloo, about 50km east of Perth, started around 2pm on New Year's Day and has burnt through 726 hectares.
It is stationary but has not been contained or controlled.
There were reports that at least one home was lost, but WA Department of Fire and Emergency Services spokesperson Lauren McDonnell said this had not yet been confirmed.
Firefighters are battling to contain a blaze east of Perth burning since New Year's Day. (HANDOUT/DEPARTMENT OF FIRE AND EMERGENCY SERVICES WA)
"Our urban search and rescue teams are heading out to do rapid damage assessment, and once they've done that, we'll be able to confirm," she said.
WA's biggest correctional centre, Acacia Prison, is in the danger zone and the nearby minimum-security Wooroloo Prison Farm is also on alert.
"In terms of concerns to the prisons, DFES is in regular contact with Corrective Services and WA Police, and we're pretty confident that the prisons are going to be fine," Ms McDonnell said.
Footage from a news helicopter showed flames moving through paddocks, structures alight and the blaze coming close to Acacia Prison.
The fire was downgraded to watch and act around 7pm on Wednesday but a possible threat to lives or homes remains, according to an Emergency WA alert issued on Thursday.
The Great Eastern Highway was shut at the height of the danger but opened overnight.
09:01 AM - Bushfire Watch and Act - MONITOR CONDITIONS - THE LAKES, WOOROLOO and WOOTTATING: — DFES (@dfes_wa) https://t.co/dh3YtI2ctWJanuary 2, 2025
An evacuation centre has been set up at the Northam Recreation Centre, with locals urged to bring medications and identification.
Extreme fire danger alerts have also been issued across the state's south on Thursday, including the Esperance coastal area which is popular with holiday makers.
Total fire bans have been declared for dozens of local government areas in Western Australia.
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