Ms. White said she had no idea what charges, if any, had been lodged against her son.
She said that before her son’s last visit to Iran, he underwent chemotherapy and radiation treatment for a neck tumor. He also suffers acute asthma, she said.
The Iranwire account included a link to a Google cache of photographs that included Mr. White and a woman described as his Iranian girlfriend, who was not further identified. Ms. White confirmed the photos showed her son.
Asked for comment, a State Department official said in an emailed response: “We are aware of reports of the detention of a U.S. citizen in Iran. We have no higher priority than the safety and security of U.S. citizens abroad. Due to privacy considerations, we have no additional information to provide at this time.”
Iran’s United Nations mission in New York did not immediately respond to a request for comment.
There has been no mention of Mr. White’s incarceration in Iran’s state-run press, but that would not be unusual. The Iranian authorities did not publicize the imprisonment of another American, Xiyue Wang, a Princeton graduate student, for nearly a year before disclosing it in July 2017.
The prisoner issue has long added to the tensions between Iran and the United States. The last time Iran released any imprisoned Americans was when the nuclear agreement took effect in January 2016. The Iranians released four Americans, including Jason Rezaian, the former correspondent for The Washington Post. The United States released several Iranians held on sanctions violations.
Besides Mr. White and Mr. Wang, Iran is also known to be holding Siamak Namazi, a businessman, and his father, Baquer Namazi, a former diplomat for the United Nations Children’s Fund. Both are naturalized American citizens.
In addition, the United States has repeatedly asked Iran for information concerning the whereabouts of Robert A. Levinson, a former F.B.I. agent who disappeared in the country in 2007. His family in the United States has held out hope that he is alive.