The town of Harvey is actively under threat from a massive bushfire tearing through the South West of WA, which has already destroyed almost 100 homes.

Key points: About 95 houses lost in Yarloop plus a number of other structures, including some historical buildings

About 95 houses lost in Yarloop plus a number of other structures, including some historical buildings Emergency situation declared for shires of Harvey, Waroona, Myalup, and surrounding areas including Preston Beach

Emergency situation declared for shires of Harvey, Waroona, Myalup, and surrounding areas including Preston Beach Up-to-date alerts on the DFES website and emergency information 133 337

Up-to-date alerts on the DFES website and emergency information 133 337 Evacuation centres set up at Murray Leisure Centre, Pinjarra and Leschenault Leisure Centre, Australind

Three people from Yarloop who were unaccounted for have now been found, in the blaze which has burnt more than 58,000 hectares and is threatening more towns south of Perth, after breaching containment lines.

Conditions have been "extremely difficult", with the blaze unpredictable and fanned by heavy wind gusts, WA Fire and Emergency Services commissioner Wayne Gregson said.

"I believe we've had what I would suggest [are] catastrophic losses within Yarloop," he said.

"These are, as yet, to be definitively confirmed figures, but it appears that we've lost around 95 houses, a number of structures within the town site including some of the historical buildings, the workshops, some factories, and an impact at 70 per cent on the demountable component of the local school," he said.

"Also losses to post offices, adjacent stores and our own fire station infrastructure."

Department of Fire and Emergency Services incident controller Greg Mair briefed a crowd of about 600 people at the Australind evacuation centre.

He said the fire was likely to continue burning south-west towards Myalup, possibly reaching Binningup, north of Bunbury.

Mr Mair said rain that fell in the area did not have any effect on the fires.

He said firefighters were battling extremely strong winds and more than 4,200 homes were without power in the region.

Mr Mair said 100 people stranded on Preston Beach were unable to be evacuated, with WA Police officers assisting them.

Up to 100 people stranded in Yarloop have been evacuated by fire crews through a road convoy of 30 vehicles, which was deemed safer than an aerial evacuation.

'People don't yet know what's happened to their houses'

Acting Premier Kim Hames addressed the meeting, announcing disaster assistance of up to $3,000 for those affected by the fires.

Dr Hames said emotions were running high as people waited anxiously to learn the fate of their homes and livestock.

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"People don't know yet what's happened to their houses, to their farms, to their stock, to their pets and it's a very trying time," he said.

"You can't let people back in because the risks are too great."

Emergency Services Minister Joe Francis addressed rumours of a shortage of water in Yarloop overnight.

"It doesn't really matter whether the power went out to pumps or the pumps were destroyed or the tanks were emptied, it was limited resource. You just have to keep that in mind," he said.

"If you're out in regional Western Australia if you want to stay and defend you need your own water supply, you need your own power supply."

Mr Gregson said "three or four" firefighting personnel had sustained slight injuries and a fire truck was also destroyed at Lake Clifton.

He said conditions were fierce and the blaze was "uncontrolled" and "very unpredictable".

"You get fires to a certain stage of intensity, where it makes little difference," he said.

"It would be like tipping a glass of water on a roaring bonfire. You can get to the stage where your suppression activity is not going to make a significant difference to the fire suppression efforts."

Evacuees at the Pinjarra emergency centre, who fled the flames, were ordered inside after a 75-year-old man was struck by lightning.

At least one major strike hit a tree near the centre, while an ABC camera operator was also almost struck.

The 75-year-old man was released from hospital on Friday night after being treated.

The NSW Rural Fire Service said 60 firefighters would travel to WA to help local fire crews, some of whom have worked 30 hours straight to battle the blaze.

Fire disaster a 'catastrophe': insurance council

The Insurance Council of Australia has labelled the disaster a "catastrophe".

Council spokesman Campbell Fuller said initial estimates put the value of insured losses in the tens of millions of dollars.

He said the catastrophe declaration meant urgent attention and priority for those who have lost property in the fires.

"The stress that people are under means the name of the insurer they're with isn't necessarily at the top of their mind," he said.

"So by calling that hotline we can help them track down that insurer they're with and steer them in the right direction to lodging a claim."

Western Power said about 3,900 properties remained without power in the fire-affected area because of the bushfire.

"At present Western Power crews cannot access the fire-affected areas because the area is still unsafe," the utility provider said.

"Western Power is expecting significant rebuilding of the network will be required based on the size of the fire zone and the number of assets in the area."