North Korea has detained another U.S. tourist, bringing to three the number of American nationals known to be held in the country, diplomatic sources said Thursday, according to Kyodo News.

The man, who was part of a tour group, was brought into detention in mid-May shortly before he was about to leave North Korea, according to the sources. A U.S. Department of State official said the department was aware of a third American reportedly being detained in North Korea, Kyodo News reported.