About 20 structures at ranches and properties north of the fire were threatened but weren't in imminent danger, said Gary Roberts, a spokesman for the Southwest Area Incident Management Team, which was fighting the fire.
Those structures included homes, barns and sheds.
People from one of the ranches voluntarily left the area, but they weren't evacuated, Roberts said.
About 440 firefighters were battling the Willow fire, which was burning cypress trees, chaparral and brush in harsh terrain in the Tonto National Forest.
Five helicopters, four bulldozers and two engines also helped with firefighting efforts.
The Mazatzal Wilderness Area was closed to the public along with two nearby roads.
The Federal Emergency Management Agency approved a request for funds to help firefighting efforts Monday.
Arizona's Division of Emergency Management also sent a hazardous assessment officer to the fire Monday to help evaluate the threat.
The fire was started by lightning on Thursday.
