The American who crossed the border from South Korea to North Korea without authorization Tuesday is a U.S. soldier, a U.S. official has confirmed to POLITICO.

The crossing and presumed detention of the American, who has not been named, was announced Tuesday morning in a tweet from American-led United Nations Command in the Korean Peninsula.

“A U.S. National on a JSA orientation tour crossed, without authorization, the Military Demarcation Line into the Democratic People’s Republic of Korea (DPRK),” U.N. Command tweeted Tuesday. “We believe he is currently in DPRK custody and are working with our KPA counterparts to resolve this incident.”