A bushfire which threatened lives and homes south of Western Australia’s largest regional city is being treated as suspicious.

Hundreds of residents in Dalyellup, 15 minutes south of Bunbury, were evacuated on Saturday afternoon after the blaze reached an emergency level warning.

Up to 80 career and volunteer firefighters were actively defending homes after the bushfire started at 2pm, with 60 still at the scene on Sunday afternoon.

Water bombers were sent in to support from above and more than 250 hectares of land has been burnt.

Gelorup resident Terri Sharp lives one kilometre from where the bushfire started and was lucky to not have to evacuate.

She took photos of the thick smoke from her driveway.

“Suddenly it started to turn black and … as the smoke increased it started to billow those really angry, volcanic eruption kind of clouds,” Ms Sharp said.

“It was pretty scary when you see it, and it was pretty close.

Firies praised as investigation underway

Bunbury detectives are investigating the cause of the blaze, with assistance from the arson squad.

It comes nearly two weeks after police started a separate investigation into two bushfires that destroyed a house and threatened other properties in South Bunbury.

The home was destroyed after embers from the blaze several streets away were sucked into an evaporative air conditioning unit and sparked a fire in the roof.

WA Police are urging anyone who witnessed suspicious behaviour in Dalyellup or South Bunbury in recent weeks to contact Crime Stoppers.

Ms Sharp praised the firefighters’ efforts to get the Dalyellup blaze under control overnight.

“It’s very humbling to know that there’s men and women out there risking their lives, fighting the fire to protect people,” she said.