A wildfire burning in southern Arizona has spread to 4,200 acres Saturday evening and is 10 percent contained. The National Weather Service in Tucson said smoke from the fire was visible on radar. A release from the U.S. Forest Service says the Cumero Fire ignited around 9:30 a.m. Friday next to Cumero Mountain, about 10 miles northeast of the Arizona border town of Sasabe. The fire is mostly in the Coronado Forest, but has also burned several hundred acres of the Buenos Aires National Wildlife Refuge. So far no structures have been damaged. 165 personnel, including five wildland fire crews and five engines, had been assigned to the scene, expanding from the crews that were on scene Friday. Assisting them are now three helicopters, which are dropping water to slow the fire's progress. Winds throughout the day Friday helped the fire spread among grass and brush, and authorities said the fire's future growth potential remained high as of Saturday evening. Officials from state, federal and local agencies responded to the scene. Authorities said the fire was caused by human activity, and was under further investigation.