The U.S. State Department said on May 7 that it was aware North Korea has detained another American citizen on suspicion of acting against the state.
Kim Hak Song, who was detained on May 6, worked for the Pyongyang University of Science and Technology, the North's KCNA news agency said.
"A relevant institution is now conducting a detailed investigation into his crimes," it added.
The U.S. State Department said in a statement that it was "aware of reports" that a U.S. citizen was detained in North Korea.
"The security of U.S. citizens is one of the Department's highest priorities. When a US citizen is reported to be detained in North Korea, we work with the Swedish Embassy in Pyongyang, which serves as the United States' Protecting Power in North Korea," the statement added.
Three other U.S. citizens are currently being held in North Korea, including Kim Sang Dok who was reportedly detained in late April for hostile acts.
The arrest comes amid rising tensions between Washington and Pyongyang over North Korea’s nuclear and missile programs.