An elderly U.S. citizen whose son was arrested in Iran last fall has also been detained in Tehran, his family said Wednesday.

Baquer Namazi, 80, was arrested Monday evening and apparently taken to Tehran’s Evin prison, according to a Facebook posting by his wife, Effie.

Their son, Siamak, an Iranian American businessman based in Dubai, has been held by Iranian security authorities since October. It is not clear what crime he is accused of committing, and no charges in his case have been announced.

In an open Facebook message to friends and relatives, Effie Namazi wrote that neither she nor a family lawyer has been able to get more information about the circumstances behind her husband’s arrest.

Iranian American Siamak Namazi is pictured in Germany in 2015. His 80-year-old father was arrested in Tehran on Feb. 22, 2016. (Reuters)

“Now both my innocent son Siamak and my Baquer are in prison for no reason,” she wrote. “This is a nightmare I can’t describe.”

Bijan Khajehpour, who is married to Baquer Namazi’s niece, said the family would make no further statement.

The Iranian lawyer, Mahmoud Alizadeh Tabatabei, told the Associated Press on Thursday that he does not believe the elder Namazi will face “political charges,” and is being held “for some investigation only.”

“It is unlikely that he will be charged,” the lawyer told AP.

Baquer Namazi has a heart ailment and other conditions requiring medication, his wife wrote. She described herself as “extremely concerned and worried sick” about his health.

Her husband was a prominent official during the rule of the shah, who was toppled in the Islamic revolution of 1979. Namazi, a former governor of the oil-rich province of Khuzestan, was allowed to leave Iran with his family in 1983 and immigrate to the United States. He subsequently moved permanently back to Iran. Most recently, Namazi was the head of Hamyaran, a group of Iranian nongovernmental organizations.

His son worked for Crescent Petroleum in the United Arab Emirates.

Mark Toner, the State Department’s deputy spokesman, said he was aware of reports that another U.S. citizen had been detained in Iran but cited privacy considerations in declining to say more.

“The U.S. Department of State has no higher priority than the protection of U.S. citizens overseas,” he said. “We take our obligation to assist U.S. citizens abroad seriously.”

The arrest of the family patriarch comes days before Iranians go to the polls to elect a national parliament and the Assembly of Experts, a group of mostly elderly clerics tasked with picking a new supreme leader when the ailing Ayatollah Ali Khamenei dies.

Last month, Iran released five U.S. citizens, including Washington Post reporter Jason Rezaian. Most were part of a prisoner deal arranged over months of negotiations, but Siamak Namazi was not in the group.

“I pray to God that my Siamak and Baquer return home to me and that they are released,” Effie Namazi wrote. “Please keep them in your prayers.”