A 2,000-acre brush fire was burning Wednesday night near Sonoita and closed part of Arizona 83, officials said.
The Oak Tree fire was burning grass and brush near milepost 42. It was burning about 10 miles north of Sonoita.
The fire was 20 percent contained and wind gusts up to 30 mph Thursday may hamper firefighting efforts, said Michelle Fidler, a National Park Service spokeswoman.
The fire was burning southwest Wednesday night, and the wind may change its direction to the northeast Thursday, Fidler said. She said the nearest structure was about five miles away.
Ground crews worked along Arizona 83 to strengthen the fire line along the west, and also along Empire Ranch Road on the south to help keep the fire north of that road, Fidler said.
Crews will monitor the fire throughout the night.
The highway was closed between Sahuarita Road and the Arizona 82 and 83 junction, due to the active fire, said Quentin Mehr, an Arizona Department of Public Safety spokesman. One lane may open by Thursday morning, he said.
It was determined that the fire was human-caused, and it was reported at 1:15 p.m., said Fidler.
One-hundred firefighters were assigned to the blaze by Wednesday night, and four water tenders were on site. Five planes and two helicopters worked the fire just before nightfall, Fidler said.
Ground crews working the fire include the U.S. Forest Service, Patagonia Fire Department, Whetstone Fire District, Mescal-J6 Fire District, Sonoita-Elgin Fire District and Arizona State Forestry Division.
This is the second brush fire in two days in this area.