UPDATE: LIGHTNING is believed to have started the bushfire on Doubtful Island Peninsula in WA, where people have fled to the beach.The Department of Environment and Conservation urged people in the area, east of Bremer Bay, to flee to the coast as lives, houses, shacks and campsites come under threat.
"You are in danger and need to act immediately to survive," the DEC said.
A local resident told AAP the bushfire appeared to have been started by a lightning strike, but that was yet to be confirmed.
The emergency warning is separate from the blaze that threatened Bremer Bay earlier this week, which was also caused by lightning.
The DEC said the bushfire was moving fast, driven by west northwesterly winds.
Incident controller Roger Armstrong said firefighters would try to trap the bushfire on the peninsula before the wind changed direction over the weekend.
"We're currently moving machinery down towards the fire and with the current wind direction, it will confine it to the peninsula," Mr Armstrong told ABC radio.
Shire of Jerramungup chief fire control officer Wes Thomas told the broadcaster that volunteer marine rescue services were on stand by to pick up people on the beach in case they became trapped.
"They are reasonably safe at this stage."
Motorists have been advised to avoid the area.
Doubtful Islands Road and local tracks are closed, and firefighters are building containment lines.
Separately, the DEC gave the all clear for people in the Bremer Bay and Quaalup townships, saying the bushfire in the area earlier this week was now under control.