Three people are missing after blaze sparked by lightning wipes out town.

The historic West Australian town of Yarloop, south of Perth, will be rebuilt after a bushfire wiped out at least 121 homes.

Colin Barnett met residents at the Pinjarra evacuation centre yesterday and said the state government would help rebuild public facilities at Yarloop, but was unsure how many of the 545 people would return.

"I'm sure there will be a Yarloop, but probably not a Yarloop of its previous size," he said.

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Department of Fire and Emergency Services commissioner Wayne Gregson said it had been a challenging bushfire and they were "not out of the woods yet".

"I don't like to get optimistic in these circumstances, we'll just see what time brings," he said.

"We're seeing conditions that we've not seen before on this type of fire, particularly when it went through Yarloop."

The premier also announced disaster assistance for victims under the jointly funded Commonwealth-State Natural Disaster Relief and Recovery Arrangements.

Barnett said he was in awe of emergency services and admired the spirit of residents.

There will be a review into the bushfire, which has burned more than 70,000ha, he said.

Federal MP Andrew Hastie also visited the evacuation centre and said the Prime Minister wanted to convey his sympathy to the victims and admiration for those helping.

Three people are still missing, but authorities hope to find them alive.

Four firefighters have also been injured since lightning sparked the fire started on Wednesday.

More than 60 New South Wales firefighters arrived on Saturday and will help fatigued crews.

In addition to the lost homes, several other structures were razed in Yarloop, including part of the school and the 110-year-old Yarloop Workshops and Steam Museum.

Almost 100 people were evacuated from Yarloop by air and road after the devastation, but 16 refused to budge, including Ron Sackville, who told AAP on Friday that he heard gas bottles and petrol drums explode as properties around him burned.

"Once it hit the town there was no stopping it because the houses were just exploding," he said.

An emergency warning is in place for areas east of Waroona, Hamel, Cookernup, Yarloop, Harvey and surrounding areas, but not for Waroona.

A "watch and act" alert remains for an area bounded by Preston Beach, Lake Clifton and north of Waroona, and an area bounded by Waroona in a line west to the coast, as well as Myalup.

Several roads and recreation sites remain closed, and dairy farmers have been forced to dump thousands of litres of milk.

Western Power says thousands of properties remain without power but burned trees and debris in danger of collapsing must be cleared before crews can rebuild the network.

About 835 people have registered at two evacuation centres. Material donations are not being officially accepted, but essentials and small gifts have been given to those in need, and animals have been provided with shelter.

People can make monetary donations through the Lord Mayor's Distress Relief Fund and the state government has already committed A$1 million.

- AAP