The DPRK has detained another American citizen on suspicion of acts against the state, reported the country's KCNA news agency on Sunday.
Kim Hak Song, who was detained on May 6, worked for the Pyongyang University of Science and Technology, according to the report.
Four US citizens arrested so far
Kim is the fourth US citizen detained by the DPRK so far.
Less than a week earlier, KCNA confirmed that Pyongyang detained a US citizen in April for allegedly carrying out a "hostile action."
The American national, identified as Kim Sang Dok, was arrested at Pyongyang airport for committing "hostile criminal acts with an aim to subvert the country."
Last year, two other Americans were arrested and are currently serving hard labor sentences in the country.
Otto Warmbier is taken to the DPRK's top court in Pyongyang on March 16, 2016. /Kyodo Photo
Otto Warmbier, a 22-year-old student, was detained in January last year and sentenced to 15 years of hard labor by a DPRK court for attempting to steal a propaganda banner.
Kim Dong Chul attends a news conference in Pyongyang on March 25, 2016. /VCG Photo
In March 2016, Korean-American Kim Dong Chul, 62, was sentenced to 10 years' hard labor for subversion.