Updated

South Korean prosecutors are investigating a New York University student freed this week by North Korea on suspicion he violated a law that prohibits South Korean citizens from traveling to the North without permission.

Seoul's National Intelligence Service said Wednesday that the spy agency has questioned the student, Won Moon Joo, and handed his case over to prosecutors for further investigation and possible indictment.

The 21-year-old Joo arrived in South Korea on Monday after being freed by North Korea, where he was detained for about six months after being arrested for crossing the Chinese border into the North.

South Korea's National Security Law prohibits citizens from praising North Korea or from visiting the country without approval.