WASHINGTON (Reuters) - Iranian authorities this week arrested the elderly father of an American jailed in Iran since October, the man’s family said on Wednesday.

Iranian-American consultant Siamak Namazi is pictured in this photo taken in San Francisco, California in 2006, handout photo provided by Ahmad Kiarostami. REUTERS/Ahmad Kiarostami/Handout via 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. Officials have yet to announce charges against him.

Baquer Namazi, Siamak’s father, was arrested late on Monday in Tehran, his wife Effie Namazi said in a Facebook post on Wednesday. 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.

Asked at a Senate hearing about the elder Namazi’s arrest, U.S. Secretary of State John Kerry said: “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.”

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. “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 wrote. “The lawyer also couldn’t get any information or get to see him.”

U.S. 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 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.

Baquer Namazi’s arrest comes more than a month after a high-profile prisoner swap between Iran and the United States, which saw five Americans released from Iranian prison in return for clemency for seven Iranians and dropped arrest orders for 14 others. Siamak Namazi was not released as part of that deal.

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. Iran’s judiciary spokesman said this month that most of the detained dual nationals face espionage charges.