North Korea detained another U.S. citizen on Friday, bringing the total number of Americans being held to three. The man reportedly was arrested at Pyongyang’s international airport as he attempted to leave the country, according to South Korea’s Yonhap news agency. The news agency reported the man was a professor from China who was involved with aid work in the country. Otto Warmbier, a University of Virginia student, and Kim Dong-chul, a naturalized U.S. citizen, are currently detained North Korea and are serving jail time.