May 7 (UPI) -- North Korea has detained an American teacher on suspicion of "hostile acts" against the state, according to the state-run Korean Central News Agency.
"A relevant institution of the DPRK detained American citizen Kim Hak Song on May 6 under a law of the DPRK on suspension of his hostile acts against it," KCNA said, using the abbreviation for the North's official name.
"The relevant authority is currently carrying out a detailed investigation into the crime of Kim Hak-song."
On April 22, North Korea detained another U.S. citizen, Kim Sang Duk, also known as Tony Kim, as he waited to board a flight at Pyongyang airport. He was teaching a class in international finance and management at the same university.
In 2015, Otto Warmbier, a University of Virginia student, was sentenced to 15 years of hard labor in 2016 for removing a political sign. Also that year, Kim Dong Chul, the president of a company involved in international trade and hotel services, was sentenced 10 years on espionage charges.
PUST, the only private educational institution in North Korea, has 500 undergraduate and 60 graduate students.
It began offering classes in English in 2010 to mainly children of North Korea's elite.
PUST is run by a Korean American professor and funded mainly by Christian groups.
"The mission of PUST is to pursue excellence in education, with an international outlook, so that its students are diligent in studies, innovative in research and upright in character, bringing illumination to the Korean people and the world," it says on its website.
The State Department advises Americans to not travel to North Korea, warning of "the serious risk of arrest and long-term detention under North Korea's system of law enforcement."
On Friday, North Korea accused U.S. and South Korean agents of plotting to kill Kim.