More homes are feared destroyed as more than 100 firefighters continue to battle out-of-control bushfires raging north of Perth.

The fires had already claimed 10 properties by Thursday. But Western Australia’s Acting Premier, Rita Saffioti, said there were fears on Friday the toll had grown.

“I was speaking to the (WA’s Department of Fire and Emergency Services’) Commissioner [on Friday] morning, and it was particularly difficult for a period of time yesterday. They’re going through now, assessing to see the impact,” she told Perth radio.

DFES incident controller Scott Hares confirmed the additional losses.

“We’ve completed about 80 per cent of our rapid damage assessments and we’re going to recommence them at first light,” he said.

“To those that have lost their homes, your loss is felt very firmly by us. We stand with you in these difficult and stressful times.”

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Also on Friday, DFES warned that the blazes might burn for weeks, even once controlled.

“Challenges persist as the fire burns through wetlands containing peat, which have the potential to burn underground for weeks, making the terrain unstable and unsafe,” it said in an update to social media.

The fires did ease slightly on Friday as firefighters battled to gain the upper hand.

Earlier, authorities had warned that strong winds and Perth’s searing spring heatwave meant it could be days before crews brought the blazes under control.

But, after days of temperatures nudging 40 degrees, a cool change swept through Perth early on Friday. The forecast maximum for the day was revised down to 33 degrees.

The slight reprieve in the weather had helped firefighters contain 95 per cent of the blaze but it would take some effort to get it fully under control, Chief Superintendent Metropolitan David Gill said.

“Another long night for firefighters and crews,” he told ABC Radio on Friday.

“We can’t forget the impact that’s having on the community.”

Firefighters were also concerned about a forecast south-westerly change in wind direction that would potentially threaten the previously untested northern flank of the fire, Gill said.

Crews were being stretched by the vast extent of the blaze – which has a 53-kilometre perimeter and has burned through 1800 hectares of bush – in their efforts to patrol containment lines and put out spotfires.

The Bureau of Meteorology has forecast a return of hot and stormy conditions across the weekend, which could bring dry lightning that risks igniting further fires.

It was too late on Thursday for many people to leave in eight suburbs in the City of Wanneroo and the City of Swan, in Perth’s north-east.

However, as of 8.30am local time on Friday, emergency warnings remained in place only for parts of Jandabup, Melaleuca, Wanneroo and Mariginiup thanks to lighter winds and high humidity.

The semi-rural suburb of Mariginiup has borne the brunt of the damage although residential areas in Tapping and Banksia Grove have also been hit.

Emergency WA said a fire burning at Hammond Park in the City of Cockburn has been extinguished.

More than 150 firefighters worked through Wednesday night to save homes when the massive blaze sparked in Gnangara Pine Plantation, forcing hundreds of families to leave as embers rained down.

Teams worked on Thursday to assess damage to properties so evacuated residents could be informed, with fears more destroyed homes would be found.

More than 1000 people were also left without power as critical infrastructure was brought down in unforgiving temperatures that peaked at 40 degrees, with winds of up to 80km/h fanning the flames.

East Wanneroo Primary School and Wanneroo Secondary College have been closed.