There's been a mysterious house fire on Wanneroo Road in Yokine.

Anne Naylor said the inside of the house appeared gutted and the roof had caved in too, with a mysterious message scribbled above the letterbox outside the house.

"What's pretty amazing about this is it doesn't appear to have spread very far at all, there's a lot of very long grass out the front in the garden, and that grass hasn't caught fire," she told Gareth Parker on 6PR Breakfast.