Strong winds are still forecast for Friday morning, and the Department of Fire and Emergency Services (DFES) has warned locals within the warning areas need to stay vigilant.

On Friday morning a police spokesperson told WAtoday the fire was not suspicious, however the exact cause is still being determined by DFES fire investigation officers.

Tonkin Highway has re-opened with 80km/h speed restrictions in place.

A bushfire WATCH AND ACT alert remains in place for people bounded by Rowley Road, Tonkin Highway, Ranford Road, Warton Road, Armadale Road, Liddelow Road, Gibbs Road and Nicholson Road in Banjup, Forrestdale, Harrisdale and Piara Waters in the City of Armadale and City of Gosnells.

The alert level for the fire has been downgraded because suppression efforts have contained the fire.

There is still a possible threat to lives and locals need to leave or get ready to actively defend.

The fire started about lunchtime on Thursday near the intersection of Forrest Road and Tonkin Highway.

A bushfire ADVICE alert is also in place for people in parts of Southern River, Forrestdale, Canning Vale and Banjup.

Although there is no immediate danger to people in these areas they need to be aware and keep up to date in case the situation changes.

Damaging wind warning cancelled

The Bureau of Meteorology said on Friday morning gusty winds are likely to continue especially around the Perth hills and metropolitan area, but they are unlikely to be "damaging."

Firefighters have saved a number of homes near the fire zone.

Just before 6pm on Thursday, Department of Fire and Emergency Services district officer Allen Gale told WAtoday the fire had been contained at Anstey Road.

"We've got the fire actually held at this stage at Anstey Road, south of Harrisdale," he said.

"That is really important because while the fire is still not under control there, we've managed to contain it and stop it spreading further north. We've got the water bombers available for a little bit longer [but] the firefighters are going to be busy working all night."

Mr Gale said the "risk" was still there for locals in and around the fire zone and it would be well into the evening until the department could downgrade the warning level.

More than 60 homes without power

Western Power says there are 62 homes in the fire zone which remain without power.

"We have identified damage to a number of poles with at least four of those poles requiring total replacement," Western Power said in a statement on Friday.

"Firefighters have advised us that the area is not safe enough for our repair crews to enter the fire zone.

"When it is safe for our repair crews to enter the area work will begin immediately to restore power."

John Bosco College, Harrisdale Senior High School, Harrisdale Primary School and Forrestdale Primary School will be closed on Friday as a precaution.

Mr Gale said it was unclear at this stage how the fire started, but investigations would begin on Friday morning.

He also said it was "quite likely" an out-building had been damaged in the blaze, but hopefully not totally lost.

"The full assessment will start happening tomorrow," he said.

There are reports cars and at least one shed in the fire zone may have been destroyed.

About 150 Career Fire and Rescue Service, Volunteer Fire and Rescue Service, Bush Fire Service firefighters are attending. Aerial support has been sent.

Homes, a shopping centre and other businesses were evacuated on Thursday.

Evacuation centre set up

The Department for Child Protection and Family Support has set up a temporary evacuation centre at Armadale Arena.

Speaking from the centre on Thursday night, City of Armadale Mayor Henry Zelones said there was no sense of panic among those at the facility. But Cr Zelones said he had heard unconfirmed reports of a shed lost.

"As far as we know they weren't houses, they were sheds or some other out-buildings," he said.

"There are still no confirmed losses of houses, but they are under threat."