Firefighters are working to get a grip on a wildfire north of Phoenix that has destroyed several structures including at least four homes, 10 outbuildings and two vehicles. The blaze, which was first reported Friday afternoon in the Tonto National Forest, has grown to more than 22 square miles Monday with 15% containment as crews do burnout operations. The wildfire's cause remains under investigation. Forest officials say the wildfire is burning in grass and brush. Some residents who evacuated were leaving summer homes. Crews continue to set backfires to help protect structures and other assets near Cave Creek. Firefighters are focused on suppressing flames on the fire’s northern side.