CNN  — 

A US national is believed to have been detained after crossing the Military Demarcation Line into North Korea during a Joint Security Area tour, the United Nations Command said in a tweet on Tuesday.

“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). We believe he is currently in DPRK custody and are working with our KPA counterparts to resolve this incident,” the UNC’s tweet said.

The orientation tour to the JSA, located inside the Demilitarized Zone between South and North Korea, is organized by the UNC and is open to the general public.

This story is breaking and will be updated.