The United Nations Command said Tuesday morning that an American was detained in North Korea after crossing the country’s southern border without permission.

An American citizen was on a Joint Security Area (JSA) orientation tour and crossed the Military Demarcation Line into North Korea without permission. according to To a tweet from the United Nations Command. The person is now in troubled state custody, and both North Korea and UN forces are working to resolve the case, the post continued.

The incident began when an American crossed the border while touring South Korea’s Panmunjom village, according to the Associated Press (AP). report. No further information has been provided as to why the man, believed to be a man, passed through the very noisy Demilitarized Zone (DMZ) area, and his identity has not been publicly identified.

An American on a JSA orientation tour crossed the Military Demarcation Line into the Democratic People’s Republic of Korea (DPRK) without permission. We believe he is currently in custody in North Korea and is working with KPA officials to resolve this case. pic.twitter.com/a6amvnJTuY

— United Nations Command 유엔군사령부/유엔사 (@UN_Command) July 18, 2023

The area is riddled with mines, surrounded by electric fences and barbed wire fences, with surveillance cameras and 24-hour armed guards, the BBC reported. report. According to the report, very few people choose to enter or leave North Korea through the demilitarized zone because there is a very high level of death threat for those who do.

Incident occurred just as nuclear submarine arrived at South Korean naval base in Busan, NBC News report. Tensions between North Korea and the United States are said to have escalated following the death of Otto Warmbier, an American university student who was detained in 2017. (Related: Kim Jong-un appears to have banned North Korean women from sharing his daughter’s name)

Warmbier returned to the United States before his death, but was severely abused while in North Korea and is believed to have died days after returning home. North Korean officials said North Korea was the “biggest victim” of the situation.