"An American was detained for trespassing on the border of the DPRK (North Korea) with China on January 25," the agency said in a one-sentence report. "He is now under investigation by an organ concerned."
In Washington, a US State Department spokesman said he had no knowledge of the case. South Korea's foreign ministry also said it knew nothing.
It was unclear if the reported detention had any connection with US missionary Robert Park, who was arrested on December 25.