US officials say an American soldier missing for nearly two days in Niger has been found dead. He was one of four US troops killed in a deadly ambush.

His body was found and identified Friday after an extensive search. Four Niger security forces were also killed.

The Department of Defense on Friday also identified the first three Green Berets killed as Staff Sgt. Bryan C. Black, 35, of Washington; Staff Sgt. Jeremiah W. Johnson, 39, of Ohio; and Staff Sgt. Dustin M. Wright, 29, of Georgia.

The name of the fourth Green Beret killed has yet to be released.

US officials say they believe extremists linked to ISIS were responsible for the attack about 200 kilometers north of Niger’s capital of Niamey.

The joint patrol of US and Niger forces were leaving a meeting with tribal leaders and were in trucks. They were ambushed by 40-50 militants in vehicles and on motorcycles.

Eight Niger soldiers and two US troops were wounded. The officials weren’t authorized to discuss the matter publicly and spoke on condition of anonymity.