Four children, the youngest just eight, are being questioned over a suspiciously lit fire in Middle Swan yesterday.
Police confirmed three youths aged 12, 10 and 8 from Middle Swan and a 14-year-old from Swan View were in custody last night but no charges had been laid.
Firefighters had to seek air support to battle the blaze near the Perth SpeedDome and Moorditj Noongar Community College.
The fire was reported about 12.40pm and burnt through scrub near Roe Highway and Eddie Barron Drive.
A Department of Fire and Emergency Services spokesman said 10 fire trucks fought the blaze, which was brought under control by 2pm.