Earlier on Friday, Japan's Kyodo news agency reported that North Korea had detained a U.S. citizen in mid-May, bringing the number of Americans being held by the reclusive state to three. The Kyodo report quoted unidentified diplomatic sources.
In April, the North said it was holding an American named Matthew Todd Miller who had made "a gross violation of its legal order" after entering the country on a tourist visa.
North Korea is also holding Kenneth Bae, a Korean American missionary who was arrested in 2012 and has been sentenced to 15 years of hard labor on charges of state subversion.
North Korea has twice canceled visits by Robert King, the U.S. special envoy for North Korean human rights issues, to discuss Bae's case.
The United States has no diplomatic ties with North Korea and the interests of its citizens in the country are represented by Sweden, which has an embassy in Pyongyang.
North Korea has detained and then released other Americans in the past year, including Korean War veteran Merrill E. Newman.