A US Navy veteran has been held in an Iranian prison on unspecified charges since July, his mother told The New York Times on Monday.
Michael R. White, of Imperial Beach, California, was detained in Iran while visiting his Iranian girlfriend, the mother, Joanne White, told The Times.
The mother filed a missing-person report after her son failed to return as planned in late July, and State Department officials told her three weeks ago that he was in an Iranian prison, she told The Times.
A duty officer reached at the US State Department early Tuesday said the department's media team could not comment on the report due to the ongoing partial government shutdown.
CNN also has sought comment from the governments of Iran and Switzerland, which represents the United States' diplomatic interests in Iran.
Tensions between Iran and the US have increased after the US withdrew from a nuclear deal with the Islamic republic in May and reinstated sanctions against it.