WASHINGTON — A fourth U.S. soldier was killed in an attack this week on a joint U.S. and Nigerien patrol, the Pentagon confirmed Friday.

Officials at U.S. Africa Command on Thursday said three soldiers had been killed and two others were wounded in the attack Wednesday in southwest Niger. Also killed was one partner nation soldier.

News about the fourth death was first reported Friday afternoon by Fox News.

Information about a fourth soldier was not announced Thursday because an ongoing rescue effort was underway to find the soldier, whose duty status was marked unknown, according to officials at U.S. Africa Command.

On the day of the attack, about a dozen U.S. special operators and a platoon-sized element of Nigerien forces were conducting a vehicle mounted patrol “to establish relations with local leaders,” said to Col. Mark Cheadle, a spokesman for AFRICOM.

The patrol came under heavy enemy fire, and U.S. forces responded, killing the enemy forces, Cheadle said.

U.S. forces didn’t have armed aircraft overhead during the onset of the mission, Cheadle said, but the patrol was being watched by overhead drone assets.

Following the attack, French aircraft quickly responded when they were notified of a need for air power for U.S. and Nigerien forces on the ground, Cheadle told reporters on Friday. But no airstrikes were actually conducted.

In the aftermath of the attack, U.S. forces launched a massive rescue effort for the fourth soldier that involved “more than 100” rescue and recovery personnel, Cheadle said. The effort involved multiple commands, U.S. special operators, signals intelligence, human intelligence, and other U.S. forces including U.S. Navy Seabees.

Nigerien forces eventually found the body of the fourth U.S. soldier, Cheadle told reporters. The body was transported by Nigerien forces, where they met up with U.S. special operations forces and handed over the body.

The body of the U.S. soldier was treated and held with the utmost respect by Nigerien forces, Cheadle said.

The body was transported by U.S. aircraft to Niger’s capital of Niamey, where it was identified, Cheadle said.

According to Cheadle, U.S. officials believe they know who carried out the attack but are not prepared to release that assessment in an effort to deny the enemy force any notion of success from the attack.

But, Niger hosts a multitude of Islamist insurgencies and terrorist groups to include al-Qaeda in the Islamic Maghreb, or AQIM, Boko-Haram, and the Islamic State in Greater Sahara, or ISGS.

In addition to the four U.S. deaths, local Nigerien news outlets have been reporting that four Nigerien soldiers also were killed in the Wednesday attack, bringing the possible death toll to eight.

The incident is still being evaluated.

“We will get to the bottom of this,” Cheadle said.