A major bushfire that destroyed property on Boxing Day is suspected to have been deliberately lit

West Australian Premier Marc McGowan issued a blunt warning to anyone caught deliberately lighting a fire as one man was charged.

Police are investigating the “suspicious” origins of a bushfire that tore through bushland east of Perth on Boxing Day, destroying one home.

Emergency warnings remained in place on Monday for residents of Wooroloo and Chidlow in the shire of Mundaring as embers from the blaze threatened nearby properties.

“We wouldn’t determine the exact cause of it yet, we’re only determining that we believe it to be suspicious at this stage,” a Western Australia Police spokesperson said.

The fire is believed to have started near the intersection of Old Northam Rd and Government Rd in Beechina.

Meanwhile, police have also charged a 42-year-old man with deliberately starting fires in the Byford area of Perth on Christmas Day that burned 30,000 square metres of bushland.

The man remains in custody and will face court on December 31.

WA Premier Mark McGowan warned that those deliberately lighting fires would be caught and sent to jail. Picture: Evan Collis

Premier Mark McGowan said those who deliberately lit fires put lives and homes at risk and would be caught.

“Police are very effective at tracking people who do this. If you want to light a fire, understand that there’s a strong chance you’ll be caught and you’ll go to jail,” Mr McGowan said.

“This is a very serious offence, particularly in the weather we’re going through.”

Another fire that threatened homes on Boxing Day in Margaret River has been downgraded to a watch and act, with authorities confirming the blaze is contained without any loss of property.

WA Police Commissioner Chris Dawson appealed to the community for any information on how either of the fires began.

Firefighters battle bushfires at Yanchep in Western Australia. Picture: Evan Collis

El Caballo Golf Course owner Ian Tapper – who was about 5km northeast of the Wooroloo fires – said fire services had dropped in on Sunday to pick up some water from his dams.

“The choppers yesterday come in, get a bit of water from one of my dams. About half a dozen loads,“ he said.

“If you can help save someone’s house … who knows when it might be yours next?”

Mr Tapper said he hadn't noticed any huge sense of panic in the community, although his business was isolated from the nearby towns of Wooroloo and Chidlow.

“A lot of people out here are pretty used to (the fire conditions),” he said.

By Monday lunchtime, there was little evidence from his vantage point that there were even fires in the region.

“There’s not a lot of smoke in the air, can’t really smell it either – a bit of wind coming from the east,” he said.

Bushfires at Yanchep earlier in December. Picture: Evan Collis

Mr McGowan thanked the hundreds of firefighters, many of them volunteers, who gave up their holidays to battle blazes.

“These people have been risking their lives to save homes, properties and animals that belong to complete strangers,” Mr McGowan said.

“It has been a phenomenal effort in horrific conditions. There’s no doubts these efforts have saved many, many people’s homes.”

A total fire ban remains in place for all affected and surrounding areas.

Perth is expected to reach a top of 41C on Monday, with the mercury to stay above 30C all week.