Sixty firefighters are still battling a bushfire that threatens lives and homes about 50km south of Perth.

The fire, which started about lunchtime yesterday, has so far burnt 150 hectares of bushland in the Rockingham Lakes Regional Park and is moving slowly.

A spokeswoman for the Fire and Emergency Services Authority (FESA) said the fire was contained but not controlled, with flames about one metre high.

FESA has warned the bushfire could possibly threaten the lives of people in the nearby suburb of Karnup, which it is approaching.

So far firefighters have saved homes and sheds in areas near the Rockingham Lakes Regional Park while the Marapana Wildlife World and a service station have also been saved.

The fire has burnt several power poles which has caused blackouts to some homes in Karnup and Western Power is working to replace the burnt poles and restore power.

Several roads have been closed including Fletcher Road and Paganoni Road, while train services along the Mandurah Line have resumed.

Overnight 120 firefighters were fighting the blaze with the help of helicopters and fixed wing water bombers, which were called in during daylight.