North Korea said Saturday that a South Korean man who it said was a student at New York University had been arrested and charged with illegally entering the country, New York Times reported.

The North’s official Korean Central News Agency said that the student, Joo Won-moon, 21, from New Jersey, was detained on April 22 in North Korea after crossing the Yalu River from the Chinese town Dandong.

The river forms part of North Korea’s border with China.

Joo, who is said to hold permanent resident status in the United States, admitted violating North Korean law, said the news agency, which added that an investigation was continuing.

The South Korean government said it could not immediately confirm the North Korean news report.

A student who identified himself as Won Moon Joo wrote on a web page for an introductory computer science course at N.Y.U. in the fall of 2013 that he was a sophomore finance major from Seoul, South Korea. It was unclear whether that student was the one detained in North Korea.