Bushfire watch and act alert for Midwest

A watch and act bushfire alert has been issued in Western Australia's Midwest region, where an out-of-control blaze poses a possible threat to lives and homes.

The alert applies to the northern part of Eradu South in the City of Geraldton.

The cause of the fire, which was reported about 6.30pm on Monday, is unknown.

Meanwhile, firefighters have again contained a fire that had threatened lives and homes in Perth's southern suburbs after the blaze jumped containment lines.

The fire has been downgraded to an advice after a watch and act alert was twice issued for people in the southern part of Coolbellup in the City of Cockburn on Tuesday.

The advice now stands for the western part of neighbouring Bibra Lake.

Emergency services have controlled the fire, which forced the evacuation of the independent Perth Waldorf School.

The cause of the fire, which was reported at 6.15am, is unknown.