Authorities are warning residents in several Western Australian towns that could be hit by a bushfire within hours to evacuate immediately unless they are ready to actively defend their homes.
The Department of Fire and Emergency Services (DFES) said the situation had escalated and the towns of Harvey, Cookernup, Wokalup and surrounding areas could be hit within hours.
An emergency warning also remains in place for east of Waroona, Hamel and the Harvey town site, while a watch and act remains in place for Preston Beach, Myalup and Waroona town site.
There are now four people unaccounted for in the bushfires that have torn through more than 70,000 hectares in the state's South West.
DFES told a community meeting the number had increased from three. It is believed they are all from the town of Yarloop, which was devastated by the blaze.
WA police would not confirm the increase, but said the number of people reported as missing was variable.
The number of homes in Yarloop destroyed by the blaze has risen to 131, with authorities saying that number would no doubt continue to rise.
The blaze started on Wednesday and has so far burnt through 70,000 hectares of land. Its perimeter stretches for more than 222 kilometres.
Commissioner Gregson said it had been a very challenging fire.
"We're seeing conditions that we've not seen before on this type of fire, particularly when it went through Yarloop," he said.
"We've got additional resources coming in not because we don't have the capability or the capacity here, it's just around fatigue management.
"There's some very tired firefighters out there in need of some relief."
Commissioner Gregson believed the fire response had been well co-ordinated.
"It's still a challenge. We're not out of the woods yet," he said.
Around 100 residents left in Yarloop on Thursday night were earlier escorted to an evacuation centre in Pinjarra.
Dairy farmers from across the region have already dumped thousands of litres of milk, with processor Harvey Fresh without power since Thursday.
About 250 firefighters are working on the fire perimeter which is more than 220 kilometres, with dozens more from the New South Wales Rural Fire Service arriving today.
Situation still very dangerous
WA Premier Colin Barnett said although conditions had improved, it was still a very dangerous situation.
He praised everyone involved in the fire response.
"Everyone is pitching in. You see the very best of Australia when you've got a serious natural disaster such as this," he said.
Mr Barnett said he believed authorities had learnt from previous fires.
"There's no doubt the capacity of Fire and Emergency Services and also the Department of Parks and Wildlife has been substantially increased," he said.
"But what we're facing is a drier, hotter climate. So the risk is increasing year by year, but our capacity is also matching that.
"This is an extremely large fire."
Mr Barnett said the State Government had contributed $1 million to the Lord Mayor's Distress Relief Fund and urged others to donate.
He said the area had been declared a natural disaster by both the WA and Federal governments.
"That will immediately activate further support for individuals, for businesses, and particularly for Local Government, in restoring infrastructure."
The fire is believed to have taken just seven minutes to sweep through Yarloop on Wednesday night, with residents offering harrowing tales of their encounters.