Warnings downgraded, residents urged to remain vigilant as bushfires rage north-east of Perth

Emergency warnings have been downgraded to Watch and Act as bushfires continue to rage through the Swan district north-east of Perth in Western Australia.

Two derelict homes and five sheds have been destroyed in the blaze that has burned through 6000 hectares.

The Department of Fire and Emergency Services (DFES) said about 100 homes had been saved as more than 200 firefighters battled the blaze.

Firefighters are strengthening containment lines around the fire ahead of a potentially dangerous wind change.

This morning the DFES downgraded bushfire emergency warnings to Watch and Act for northwestern parts of Bullsbrook in the City of Swan and parts of the City of Wanneroo.

"It has reduced in intensity but it is still unpredictable and people need to remain vigilant," the DFES said.

Last night residents were told to leave if the way was clear but to stay put and defend their homes if it was not.

"You are in danger and need to act immediately to survive. There is a threat to lives and homes," the DFES said.

The fire started on a property between Railway Parade and Gully Road around 9am yesterday and became "out of control and unpredictable".

Yesterday a plume of smoke billowing from the fire could be seen across Perth as far away as Fremantle.

It jumped over Neaves Road and was burning in Gnangara Pine Plantation towards Wanneroo Road.

The cause of the fire is not known.

Authorities said an easterly breeze moving through the area at 30km/h all day only fueled the fire.

It is expected to continue early this morning and could reach 60km/h later today creating nightmare conditions for firefighters.

Those in their homes are urged to close all doors and windows and turn off evaporative air-conditioners, but to keep water running through the system if possible.

Those not at their properties are advised it is too dangerous to return.

Resident Todd Atkins told 9NEWS he left his home today.

"You couldn't see, you couldn't breathe, and trying to drive out we had to drive through fire," he said.

Evacuation centres have been set up at Wanneroo Recreation Centre and Gum Blossom Hall in Quinns Rock.

ROAD CLOSURES

• Neaves Road from Yanchep Road to Railway Parade 

• Railway Parade south of Stock West Road 

• Wanneroo Road between Old Yanchep Road and Hester Ave has limited access 

• Perry Road between Joondalup Drive and Wanneroo Road 

• All roads contained with the boundary of Old West Road, Kirby Road, Railway Parade, Chitty Road and Wandoo Road. 

With AAP.