The identity of the fourth U.S. soldier killed by enemy fire during a mission Wednesday in Niger was announced by the Pentagon on Saturday.

The body of the soldier, Sgt. La David Johnson, was discovered Oct. 6, the Defense Department said in a statement. He had been assigned to 3rd Special Forces Group in Fort Bragg, N.C., and was from Miami Gardens, Fla.

The incident has been under investigation since Johnson, 25, was killed with three Army Green Berets who have already been identified. The soldiers were on a reconnaissance patrol as part of what the command described as an advise-and-assist mission with Nigerien forces on Wednesday when they were ambushed by an enemy the command declined to identify. A two-day search-and-rescue effort located Johnson's body.

"The mission was not meant as an engagement with the enemy, it was meant to establish relations with the local leaders," said Col. Mark Cheadle, an Africa Command spokesman. "The threat at the time was deemed to be unlikely, so there was no overhead armed air cover during the engagement."

The ambush occurred about 124 miles north of the capital Niamey in southwest Niger, which borders Mali and Nigeria. The U.S. has several hundred troops and a drone base in the country where the Islamic State and al Qaeda splinter groups have sprouted. The military has increased its presence in that region in recent years to counter extremist groups.

There were roughly a dozen U.S. troops working with local forces, for a total mission size of about 40 troops. Cheadle said there was no indication that the Nigeriens tipped off the enemy attackers or that any foreign enemy fighters were involved.

"Frankly, at this point, I don't want to name a particular entity because I don't want to give them any sort of feeling of success," Cheadle said.

The three Green Berets killed were Staff Sgts. Bryan C. Black, 35, of Puyallup, Wash.; Jeremiah W. Johnson, 39, of Springboro, Ohio; and Dustin M. Wright, 29, of Lyons, Ga., according to the announcement. All three were assigned to the 3rd Special Forces Group based at Fort Bragg, N.C.

Dave Brown and Travis Tritten contributed to this report.