The U.S. State Department would not confirm reports on Tuesday that another American has been detained in Iran. The New York Times first reported on Monday that U.S. Navy veteran Michael White of California was arrested in July and imprisoned on a trip to visit his girlfriend.

White's mother, Joanne White, confirmed to CBS News that her son never made his scheduled return flight at the end of July, at which point the family reported him missing. She said the family only learned from the State Department in December, however, that he was being held in an Iranian prison.

"I'm very worried about his health. He just got over cancer and I'm worried about his condition. It's very scary to me," she told CBS News on Tuesday. "I know he was visiting his girlfriend. He's been over there three or four times without any issues. The last time I had contact with him was July 13th."

Get Breaking News Delivered to Your Inbox

Joanne White told the New York Times that State Department officials had told her they were seeking access to her son via the Swiss consulate, as the U.S. does not have formal diplomatic ties with Iran.

Iran is currently holding at least three other U.S. citizens, including Siamak and Baquer Namazi, and Princeton professor Xiyue Wang, in prison. The Islamic Republic has accused the three men of various crimes associated with espionage or "infiltration," but their families and U.S. officials say they are being held as leverage in the political standoff between the two nations.

CBS News senior foreign affairs correspondent Margaret Brennan notes that President Trump has often criticized his predecessor President Barack Obama for negotiating the release of American prisoners from Iran. The Trump administration has not engaged in a dialogue with the Iranians to seek the current prisoners' release.

Asked about White's case on Tuesday, a State Department spokesperson would only tell CBS News that the U.S. government was, "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."

The spokesperson said no further information could be provided for privacy reasons.

The first reports of another American being held in Iran came from the IranWire news website, which is run by Iranian nationals living outside the country. The site quoted a former Iranian prisoner, identified as Ivar Farhadi, who said he met White in October when they were both held at the same prison in the city of Mashad.

Farhadi said White had not been charged with any crime in Iran, according to IranWire.