The Marine Corps has identified a 13th MEU Marine who was reported overboard from the amphibious assault ship Essex as Cpl. Jonathan Currier.

Currier was first reported missing at 9:40 a.m. on Aug. 9 while the Essex Amphibious Ready Group was conducting routine operations in the Sulu Sea. He has officially been declared dead, according to a 13th Marine Expeditionary Unit release.

A New Hampshire native, Currier was a CH-53E Super Stallion crew chief who enlisted in the Marine Corps in 2015. He was assigned to Marine Heavy Helicopter Squadron 361 out of Marine Corps Air Station Miramar, California. He graduated from Marine Corps Recruit Depot Parris Island in November 2015.

The massive search-and-rescue operation for Currier off the Philippine coast lasted five days, covered over 13,000 nautical miles and included more than 110 sorties and 300 flight hours, the release said.

A Navy P8 Poseidon and aircraft from the Essex were used in the search, which was aided by the U.S. Embassy in the Philippines, U.S. Coast Guard, Philippine coast guard and the Singapore Information Fusion Center.

Col. Chandler Nelms, the commander of the 13th MEU, said the Marines and sailors showed “tremendous resiliency” and put forth an “extraordinary effort” during the search.

“Our hearts go out to the Currier family,” said Nelms. “Cpl. Currier’s loss is felt by our entire ARG/MEU family, and he will not be forgotten.”

An investigation into the circumstances surrounding Currier’s death is currently underway.

Marine Corps Times senior reporter Shawn Snow contributed to this report.