Arsonist destroys bus in Perth's north

A man who started a fire that caused $200,000 worth of damage to a bus that had been converted into a mobile home has puzzled WA Police.

Security footage from September shows the man, clad in black from head to toe, breaking into an industrial unit in Malaga about 2.30am before climbing onto the bus.

He proceeds to tamper with something in the roof, then climbs down and leaves the area, shortly before an explosion engulfs the front of the bus, destroying it.