North Korea has detained an American citizen who intended to fly out of the capital city of Pyongyang on Saturday. It is unclear why the individual, who was identified by the chancellor of the Pyongyang University of Science and Technology as Kim Sang-duk, was detained at the airport. “He was prevented from getting on the flight out of Pyongyang. We don’t comment further on this,” Martina Aberg, the deputy chief of mission at the Swedish embassy in Pyongyang, told CNN. Kim, a professor in his 50s who was teaching accounting at the university, is now the third American being held in the country, which has provoked international ire over its missile tests and development of nuclear weapons.