Crews are battling a large hay fire in the town of Laveen, west of Phoenix.
Phoenix Fire Department officials say the fire was reported around 4:45 p.m. Wednesday.
It's still unclear how the fire started.
Authorities say the haystack burning is 200-feet by 50-feet by 20-feet high.
It's about 1,500 feet away from a structure, but there's no report of any structural damage so far.
Phoenix Fire Capt. Scott McDonald says crews have secured water supplies and surrounded the haystack from all sides and they're working to extinguish the flames.
State Department of Environmental Quality officials also are at the scene to monitor air quality from all the smoke in the area of the fire.
People living nearby were warned to keep their windows closed.
Investigators are still trying to determine the cause of the fire.