A fire burning in southern Arizona has spread beyond a planned containment line and is expected to continue growing.
U.S Forest Service officials said Saturday the Mule Ridge Fire has grown to 8,500 acres and is 20% contained.
About 250 firefighters are working to contain the flames, which is burning in oak grassland on the north end of the Pajarito Wilderness. Four helicopters have dropped water from nearby sources and eight engines are on the scene.
The southeastern edge of the fire spread across Sycamore Canyon on Friday evening, aided by high temperatures and low relative humidity. The movement put it beyond the planned line of containment.
Crews responded by protecting structures at Bear Valley Ranch, which was in the fire's path, officials said.
Weather conditions were expected to continue to hamper fire suppression efforts.
"Firefighters have struggled with the daytime heat on this incident as ambient temperatures have created challenging conditions and the terrain is very steep and rough," officials said in an update Saturday night.
The Mule Ridge Fire started May 31 near the town of Ruby. Investigators say it was caused by human activity, but were still gathering evidence.