A U.S. soldier was killed Saturday in Afghanistan, marking the 13th American fatality there this year as the Pentagon once again ramps up operations in the 16-year-old war.

Sgt. 1st Class Stephen B. Cribben, 33, a Special Forces communications sergeant, was killed in Logar province while his unit was engaged in "combat operations," according to a U.S. military statement released Sunday. It's unclear whether his death was the result of hostile enemy contact or another event, such as a vehicle accident.

Officials are investigating the incident.

Cribben, of Simi Valley, California, was assigned to the 2nd Battalion, 10th Special Forces Group at Fort Carson, Colorado, and was just weeks into his third combat deployment when he was killed. The statement indicated that he arrived in Afghanistan in September, having previously deployed there and to Iraq as a military policeman.

He is the second Special Forces soldier killed recently in Logar province. Chief Warrant Officer Jacob Sims, 36, died in a helicopter crash on Oct. 27. A Black Hawk pilot, he was assigned to the Army's 160th Special Operations Aviation Regiment. Six other American troops were wounded in what the Pentagon described as an accident unrelated to enemy fire.

The Trump administration has sought a new strategy for the war in Afghanistan, recently approving an increase of about 4,000 U.S. troops, bringing the total deployed there to 13,500. Officials also have renewed efforts to court Pakistan and India for help countering militant activity in the region.