An American soldier was found dead this week at a base in South Korea, the military revealed Thursday.

Michael William Corey, a non-commissioned officer from Oro Valley, Ariz., was found Monday by Korean residents near Camp Jackson, a U.S. Army base near South Korea’s capital of Seoul, Reuters reports.

The military says Corey’s cause of death is unknown and it is under investigation.

Corey, an intelligence analyst, "died while conducting land navigation training at Camp Jackson," the United States Forces Korea said.

There are around 29,000 U.S. troops stationed in South Korea, according to Reuters.

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