PYONGYANG, North Korea (AP) — North Korea has detained a U.S. citizen, officials said Sunday, bringing to three the number of Americans now being held there.

Tony Kim, who also goes by his Korean name Kim Sang-duk, was detained on Saturday, according to Park Chan-mo, the chancellor of the Pyongyang University of Science and Technology.

Park said Kim, who is in his 50s, taught accounting at the university for about a month. He said Kim was detained by officials as he was trying to leave the country from Pyongyang’s international airport.

The Swedish Embassy in Pyongyang said it was aware of a Korean-American citizen being detained recently, but could not comment further.