Man questioned over WA forest fire

A 41-year-old man is being questioned by police over an out of control and unpredictable bushfire in state forest northeast of Perth.

A watch and act alert has been issued for the blaze in Julimar State Forest in the Shire of Toodyay, which was reported at 7.30am on Thursday and is being tackled by 100 firefighters.

The fire poses a possible threat to lives and homes, is moving quickly southwest and has burnt 310 hectares.

Roads have not been closed but motorists are asked to avoid the area.