A Marine sergeant whose unexplained disappearance shortly before Christmas prompted an extensive search of Joint Base McGuire-Dix-Lakehurst was found dead Saturday, the base reported.

Sgt. Tristan Clinger's body was found "in the ranges of the installation," a spokeswoman said Monday, adding that the cause of death was under investigation. He was 28.

The spokeswoman, Staff Sgt. Katherine Tereyama, declined to identify the cause of death because of the investigation.

On Dec. 20, Clinger's wife reported to police that her husband, a mechanic with Marine Heavy Helicopter Squadron 722, had walked off the base about 4 p.m. and had not returned.

When he still had not returned by Wednesday, Rachel Self Clinger posted an urgent plea on Facebook: "My husband is missing since sunday. He was last seen on Ft. Dix in NJ if anyone heard from his or sees him please contact the police right away we need to find him." She attached a photo of him wearing a red knit cap: "He was wearing this hat and a plaid button down shirt and jeans last seen. Please share this post."

She also told a Philadelphia TV station that her husband was upset when he left their home.

Her pleas prompted a search Saturday led by Missing in America, a nonprofit organization based in Bridgewater, Somerset County. The group, whose purpose is searching for missing people, drew together 47 volunteers and friends of the Clingers'. Tereyama said privacy laws barred her from saying whether the Clingers had children, or if Tristan Clinger had sought help for mental health issues.

She did say that the Marine Corps "takes the mental health of members very seriously, and offers a number of resources our people may access."

"Our men and women are our most precious resources," she said. "It's in our best interest to make sure they are mentally and physically fit to accomplish the mission."