A Black Mesa Type-1 Interagency Hotshot Crew firefighter walks through burned debris while the crew mops up along Cienega Creek east of Empire Ranch while the Sawmill Fire burns on April 27, 2017, burning in Southeastern Arizona between Green Valley and J-6.

High winds have grounded aircraft fighting the Sawmill Fire on Friday, officials said.

Fire crews continue working on the ground to fight the fire and increase containment lines around the blaze, which has burned 47,000 acres since Sunday across Southern Arizona. The fire is about 40 percent contained.

Officials say high winds expected today could hamper efforts to halt and extinguish the fire burning southeast of Tucson. High winds Thursday forced officials to ground firefighting aircraft.

The fire has already crossed one mountain range and burned across a desert valley since it started Sunday south of Tucson, about 10 miles southeast of Green Valley.

No injury or structure damage has been reported. About 800 people are assigned to fighting this fire, the largest burning in Arizona now.

An off-duty U.S. Border Patrol agent is being investigated for possibly starting the fire while shooting recreationally, officials have said.

Officials say the agent immediately reported the fire.