The soldier who has been missing since the helicopter he was on crashed off the coast of Yemen has been declared dead.

Staff Sgt. Emil Rivera-Lopez, 31, of the 160th Special Operations Aviation Regiment, was declared deceased Thursday, the Defense Department announced in a statement late Friday. He was previously listed as Duty Status Whereabouts Unknown, or DUSTWUN.

On Aug. 25, Rivera-Lopez and five other service members were on board a Black Hawk helicopter when it crashed about 20 miles off Yemen’s southern coast. The incident happened during a training mission in support of U.S. Central Command operations.

The other five service members on board were rescued by U.S. forces.

The incident remains under investigation.

Rivera-Lopez, of San Juan, Puerto Rico, joined the Army in July 2006 as a UH-60 Black Hawk helicopter repairer, according to information from U.S. Army Special Operations Command.

After training, Rivera-Lopez served in the 82nd Combat Aviation Brigade before completing the requirements to become a member of the 160th Special Operations Aviation Regiment.

Upon arriving at the regiment, Rivera-Lopez served as a MH-60M Black Hawk maintainer and squad leader in D Company, 3rd Battalion, 160th SOAR. He later was assigned to the battalion’s C Company, where he was a section sergeant and Black Hawk crew chief, according to information from USASOC.

His awards and decorations include the Air Medal (Numeral 2), Army Commendation Medal with Valor, Army Commendation Medal, Army Achievement Medal (2 Oak Leaf Clusters), Joint Meritorious Unit Award, Afghanistan Campaign Medal (3 Bronze Service Stars), Combat Action Badge, Aviation Badge and Parachutist Badge.