Iranian authorities have arrested the elderly father of an American jailed in Iran since October, the man's family said on Wednesday, according to Reuters.
Siamak Namazi, a dual U.S.-Iranian citizen, was detained by Iran's Islamic Revolutionary Guard Corps in October while in Iran visiting family, the report noted.
Now Baquer Namazi, Siamak's father, has been arrested as well. His wife Effie Namazi said in a Facebook post on Wednesday that her husband was detained late on Monday in Tehran.
The 80-year-old Namazi, also a dual Iranian-American citizen, was taken to Evin Prison, where his son is also being held, she said, according to Reuters.
Asked at a Senate hearing about the elder Namazi's arrest, U.S. Secretary of State John Kerry replied, "I am very familiar with this and I am engaged on it specifically, but I am not permitted due to privacy reasons to go into details here."
Last month, Iran and the United States agreed to a prisoner swap which saw Four American citizens being released by Iran have in exchange for seven Iranians jailed in America.
Baquer Namazi has a serious heart and other conditions which require special medication, Effie Namazi wrote in her post.
"Now both my innocent son Siamak and my Baquer are in prison for no reason. This is a nightmare I can't describe," she said, according to Reuters. "I am extremely concerned and worried sick for Baquer's health."
"I have been trying to find out more information but have been unable to do so," she added. "The lawyer also couldn't get any information or get to see him."
State Department Spokesman Mark Toner said the agency was aware of reports that a U.S. citizen had been detained in Iran.
"The U.S. Department of State has no higher priority than the protection of U.S. citizens overseas," Toner was quoted as having said. "We take our obligation to assist U.S. citizens abroad seriously."
A former Iranian provincial governor and UNICEF official, Baquer Namazi was more recently running Hamyaran, an umbrella agency for Iranian nongovernmental organizations. His son Siamak was most recently working for Crescent Petroleum in the United Arab Emirates, and previously headed a consulting business in Iran.
Iran is believed to be holding several other dual nationals, including Iranian-British citizen Kamal Foroughi, who was arrested in 2011 while working in Tehran as a business consultant.
Also still missing is Robert Levinson, a former FBI who went missing in Iran nine years ago.
The last known man to see Levinson alive in Iran has claimed that Levinson was definitely detained by Iranian authorities and is almost certainly still in Iranian custody if he remains alive.
White House spokesman Josh Earnest recently said that Levinson may no longer be in Iran, but no evidence has surfaced publicly to support that idea.