Bushfire threat in Perth's southeast eases

A bushfire in Perth's semi-rural southeast has been contained after about 130 firefighters battled the dangerous blaze overnight.

An emergency warning was issued to residents in parts of Bedfordale, Byford and Wungong in the City of Armadale on Wednesday evening and remained in place until early Thursday, when downgraded to an advice.

Authorities say there is no immediate danger to lives or homes but people in the area need to be aware and keep up to date in case the situation changes.

The fire is not yet controlled and several road closures remain.

The cause of the blaze, which has burnt 125 hectares, is unknown at this stage.

A Department of Fire and Emergency Services spokesman said firefighters had worked in a challenging environment of hills and forest.

"It's tricky terrain," he told AAP.

Cool conditions had helped and made the outlook favourable, the spokesman said.

He said there were no reports of damage to homes but one fence sustained minor damage.