A major bushfire in Western Australia's Margaret River region that has forced residents to evacuate was deliberately lit, police believe.
The blaze in the Leeuwin-Naturaliste National Park has ripped through almost 5,500 hectares since Wednesday.
Police say they believe someone deliberately lit the fire near Mammoth Cave, based on an initial assessment of the scene.
"Detectives would like to hear from anyone who saw any suspicious activity in the vicinity of Mammoth Cave on Wednesday (8 December) or who has dash-cam or mobile phone vision of people or vehicles in the area at the time," police said in a statement on Saturday.
On Saturday morning an evacuation warning was reactivated for people in the national park.
The warning area takes in an area bound by Mammoth Cave Rd to the north, Caves Rd and the Leeuwin-Naturaliste National Park boundary to the east, Grace Rd and Bridle Trail to the south and the coast to the west in the shire of Augusta-Margaret River.
In an update on Saturday afternoon Department of Fire and Emergency Services incident controller Brad Barton said the fire was now contained but not controlled.
"There's consideration at the moment to downgrade the alert levels so people need to continue to monitor the WA emergency site," he said in a livestreamed community update.
He said there were no reports of homes lost and the blaze had been mainly contained to the national park, apart from a small area around the Boranup community.
"That still remains closed unfortunately given the level of impact in and around that community ... so we're working hard to open that up as soon as possible."
Seventy-five firefighters worked to fight the blaze on Saturday, with milder weather conditions helping the containment effort.
Residents had first been urged to leave on Thursday before conditions improved on Friday, but later deteriorated.
