Wildfire managers say unmanned drones flying over wildfires could lead to firefighter injuries and force retardant bombers to be called off.
The National Interagency Fire Center in Boise says so far this year, at least three drones have flown within or near restricted airspace intended for wildfire fighting aircraft.
The center on Friday said a drone could lead fire managers to suspend firefighting efforts until it has left and managers are confident it won't return.
Spokesman Randy Eardley says drones have been spotted over fires in Washington, Oregon and Northern California.
Officials say those seeking to fly drones near wildfires need permission from wildfire managers.
The center says individuals using drones that interfere with firefighting could face civil penalties and criminal prosecution.