Aug. 7 (UPI) -- North Korea returned a South Korean national at the truce village of Panmunjom on Tuesday.
The South Korean was a man in his 30s who had "illegally entered" the North, according to South Korea's unification ministry.
"The North Korean side sent communication to us about repatriating one of our citizens at 11 a.m. on Aug. 7, after he was detained for illegal entry," said unification ministry spokesman Baik Tae-hyun, according to KBS.
The South Korean man identified only by his surname Seo had flown to China.
He then crossed into North Korea from China, but it is unclear which route he took to enter the country.
The reasons for his illegal North Korea entry are yet unknown, according to KBS. He is under investigation at the unification ministry, Seoul's spy agency and the police.
The Korea Herald reported Tuesday Seo entered the North on July 22. Seoul has described the North Korean decision as "positive from a humanitarian perspective."
In 2015, North Korea returned a South Korean New York University student, Joo Won-moon, and four other citizens.
Joo, who was 21 at the time, made headlines when he gave a press conference before foreign and local North Korean reporters in September 2015.
North Korea eventually released Joo after he said he could not find any signs of human rights abuses during his five-month stay in North Korea.