The father of Siamak Namazi, the last American citizen known to be held in an Iranian prison after the January prisoner exchange, has been arrested in Iran.

Effie Namazi, Siamaks mother, reported on Facebook on Wednesday that her husband Baquer was arrested late Monday evening in Tehran and taken to Evin prison, the same place where Siamak Namazi is being held.

Now both my innocent son Siamak and my Baquer are in prison for no reason. This is a nightmare I cant describe, Effie, who lives in Iran, wrote in a Facebook post.

Ahmad Kiarostami, a close friend of the Namazi family, told The Huffington Post that Baquer was in Dubai visiting his other son when he was told to return to Iran, where he would be granted visiting access to Siamak. But when Baquer arrived at the airport in Tehran, Kiarostami said, he was arrested by Iranian officials.

His story is similar to that of Siamak, who had been living in Dubai but traveled to Iran last July to attend a funeral. When he attempted to leave Iran and return home, he was stopped by Iranian officials , who seized his passport and told him not to leave the country. After several months of periodic interrogations, officials finally arrested Siamak in October, and he has been imprisoned since then.

Siamak has not yet formally been charged with a crime, and his family says he has not had physical access to his lawyer. His family learned through his cellmate that he had begun a hunger-strike, but he relented earlier this week after his family pleaded with him to eat.

Effie wrote on Facebook that she worried her 80-year-old husband, Baquer, would not have access to the medication he needs to treat his heart condition.

Kiarostami says that like Siamak, Baquer is a dual Iranian-American citizen. After the 1979 revolution, Baquer fled to the U.S. and gained American citizenship. Payvand news reported that Baquer began working at UNICEF in New York, and later went on to represent the organization in Somalia, Kenya and Egypt. He survived a 1994 attack by militants from an Islamic extremist group who gunned down two cars carrying U.N. officials and police officers and killed five people. Baquer was in one of the cars but was not injured.

Baquer later returned to Iran, feeling the political climate was safer than when he had fled the country the previous decade. He served as the director of a nonprofit organization called Hamyaran, which his LinkedIn account shows he was affiliated with from 1998-2009.

Once Baquer was arrested, his friends began receiving strange messages from his Facebook and Gmail accounts -- a tell-tale sign that his accounts had been hacked, and often an indication that someone in Iran has been taken into custody under suspicious circumstances. Friends of Siamak reported receiving similar messages from his accounts when he was arrested.

In January, Iranian media initially reported that Siamak was set to be freed as part of a secret prisoner agreement between the U.S. and Iran, which ultimately led to the release of four Americans in exchange for the U.S. pardoning or dropping charges against seven Iranians. But Siamak, who was arrested after the secret negotiations were nearly finalized, was not included in the deal.

Secretary of State John Kerry has said that he is continuing to push for Siamaks release, but earlier this month, Iranian-American groups wrote a letter urging him to redouble his effort. Baquers Monday arrest sends an ominous message about Siamak's prospects of being freed imminently, and could complicate Kerry's efforts to free him.

State Department deputy spokesman Mark Toner said in a statement, We are aware of reports that a U.S. citizen was detained in Iran. The U.S. Department of State has no higher priority than the protection of U.S. citizens overseas. We take our obligation to assist U.S. citizens abroad seriously. Due to privacy considerations we have no further information at this time.

For now, all the Namazi family can do is hope.

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