early start american executive detained in tehran pleitgen_00010319.jpg
early start american executive detained in tehran pleitgen_00010319.jpg
Now playing
02:11
Iranian-American businessman arrested in Tehran
A file picture shows Iranian-American Washington Post correspondent Jason Rezaian posing while covering a press conference at Iran's Foreign Ministry in Tehran, on September 10, 2013. Tehran's chief justice Gholamhossein Esmaili confirmed the arrest of Washington Post correspondent Jason Rezaian and his wife, also a journalist, the official IRNA news agency reported. Rezaian, 38, has been the Post correspondent in Tehran since 2012 and holds both American and Iranian citizenship, according to the newspaper and his wife is an Iranian who has applied for US permanent residency and works as a correspondent for The Nation newspaper based in the United Arab Emirates, the Post said. AFP PHOTO/STRSTR/AFP/Getty Images
AFP/Getty Images
A file picture shows Iranian-American Washington Post correspondent Jason Rezaian posing while covering a press conference at Iran's Foreign Ministry in Tehran, on September 10, 2013. Tehran's chief justice Gholamhossein Esmaili confirmed the arrest of Washington Post correspondent Jason Rezaian and his wife, also a journalist, the official IRNA news agency reported. Rezaian, 38, has been the Post correspondent in Tehran since 2012 and holds both American and Iranian citizenship, according to the newspaper and his wife is an Iranian who has applied for US permanent residency and works as a correspondent for The Nation newspaper based in the United Arab Emirates, the Post said. AFP PHOTO/STRSTR/AFP/Getty Images
Now playing
02:35
Freed reporter Jason Rezaian returns home
matthew trevithick on life inside iran prison_00041913.jpg
matthew trevithick on life inside iran prison_00041913.jpg
Now playing
16:49
What life is like inside Iran's most notorious prison
Ansari Family
Now playing
02:05
Freed U.S. Marine returns home from Iran
Now playing
02:31
Top U.S. negotiator: Iranian prisoner swap almost scrapped
american freed by iran speaks legal view_00000000.jpg
CNN
american freed by iran speaks legal view_00000000.jpg
Now playing
02:56
Freed American: 'I feel alive for the first time'
iran americans freed john kerry bts newday_00011829.jpg
iran americans freed john kerry bts newday_00011829.jpg
Now playing
02:18
Kerry: No connection between nuclear deal and releases
ACLU/Hekmati Family/Zero Point Zero
Now playing
02:06
Prisoners released from Iran arrive in Germany
Obama Iran Americans swap statement video_00000000.jpg
Obama Iran Americans swap statement video_00000000.jpg
Now playing
02:32
Obama: Americans are coming home from Iran
american journalist freed from iran wife speaks idaho dnt_00001429.jpg
american journalist freed from iran wife speaks idaho dnt_00001429.jpg
Now playing
02:07
Freed U.S. prisoner's wife speaks on release
Now playing
03:29
Iran frees U.S. prisoners on the heels of nuclear deal
United States Secretary of State John Kerry poses with Foreign Affairs Minister of Iran Javad Zarif during a bilateral talk at the United Nations headquarters on September 26, 2015, at the United Nations in New York.
DOMINICK REUTER/AFP/Getty Images
United States Secretary of State John Kerry poses with Foreign Affairs Minister of Iran Javad Zarif during a bilateral talk at the United Nations headquarters on September 26, 2015, at the United Nations in New York.
Now playing
02:49
American prisoners set free in Iran
iran freed prisoner wife bpr blitzer_00015119.jpg
iran freed prisoner wife bpr blitzer_00015119.jpg
Now playing
06:07
Freed American pastor's wife: It's a great, joyful day
United States Secretary of State John Kerry poses with Foreign Affairs Minister of Iran Javad Zarif during a bilateral talk at the United Nations headquarters on September 26, 2015, at the United Nations in New York.
DOMINICK REUTER/AFP/Getty Images
United States Secretary of State John Kerry poses with Foreign Affairs Minister of Iran Javad Zarif during a bilateral talk at the United Nations headquarters on September 26, 2015, at the United Nations in New York.
Now playing
00:52
Fifth American released by Iran
U.S. confirms Iran prisoner swap labott_00000000.jpg
U.S. confirms Iran prisoner swap labott_00000000.jpg
Now playing
01:30
U.S. confirms Iran prisoner swap
File photo/From Zero Point Zero
Now playing
01:11
Iran releases four U.S. prisoners

Story highlights

Siamak Namazi detained while visiting people in Tehran, reports say

He would be the first U.S. citizen reported to have been detained in Iran since nuclear deal

(CNN) —  

Iran arrested an Iranian-American while he was visiting the country this month, several U.S. news outlets reported – a detention that would bring to five the number of Americans detained or unaccounted for in the Islamic republic.

Siamak Namazi, a Dubai-based businessman with dual U.S. and Iranian citizenship, was detained while visiting relatives in Tehran, the Wall Street Journal reported Thursday, citing unnamed sources. The Washington Post also reported his detention, citing a family friend who spoke on condition of anonymity.

The Post reported that it wasn’t clear what Namazi is alleged to have done.

Namazi would be the first U.S. citizen reported to have been detained in Iran since this year’s announcement of an international agreement on Iran’s nuclear program.

CNN’s calls to the office of a spokesman of Iran’s judiciary Friday, a day when Iranian government offices are closed, were not answered.

Reports of Namazi’s capture came ahead of Friday’s multinational meeting in Austria about how to pursue peace in war-torn Syria. The United States invited Iranian officials to that meeting – a rare case of diplomatic interaction between the nations.

U.S. Rep. Mac Thornberry, a Texas Republican who chairs the House Armed Services Committee, on Friday lamented Iran’s participation in the meeting, in part because Iran is holding American citizens. He said it gives “the Iranians greater respectability on the (world) stage while they’re holding hostages as political leverage.”

“I don’t know the supposed justifications of holding him,” Thornberry, who also is a member of the House Permanent Select Committee on Intelligence, told CNN on Friday morning when asked about Namazi’s situation in Iran.

The National Iranian American Council, a Washington-based advocacy group, said Thursday it was troubled by reports that Namazi was detained.

“NIAC is very concerned by the continued detention of multiple Iranian-Americans by the Iranian government, and is deeply troubled by the reports that Mr. Namazi may also have been detained,” the group said on its website.

The detained and missing

Namazi would be the fourth American known to be currently detained in Iran, in addition to another U.S. citizen who disappeared after visiting Iran. President Barack Obama has said that his administration was working diligently to win the detainees’ freedom.

Those detained or unaccounted for include:

Amir Kekmati, a former U.S. Marine whose family says he was imprisoned just weeks after he arrived in Iran in August 2011 to visit his grandmother. Initially charged in January 2012 with espionage and other counts, he was sentenced to death. That sentence was overturned, but he was later convicted of “cooperating with hostile governments” and received a 10-year prison sentence, his family has said.

Saeed Abedini, an American Christian pastor, was detained in Iran on September 26, 2012, according to the American Center for Law and Justice. Abedini’s charges stemmed from his conversion from Islam to Christianity more than a decade ago and his activities with home churches in Iran, according to the Washington-based group. In 2013, Abedini was sentenced to eight years in prison on charges of attempting to undermine the Iranian government. He has endured torture and numerous beatings, sometimes at the hand of prison guards, the center said.

Jason Rezaian, the Washington Post’s bureau chief in Tehran, was detained on July 22, 2014, with his wife and two freelance journalists. The rest were released within months, but Rezaian was charged with espionage and crimes including “collaborating with a hostile government” and “propaganda against the establishment,” according to the Post. Iranian media reported he was convicted this month. He reportedly faces up to 20 years, but his sentence has not been specified. Both the Post and the U.S. State Department have said the charges are absurd.

Robert Levinson, a former FBI agent and contractor for the CIA who vanished after visiting Iran in 2007. Iranian officials have denied any knowledge of his whereabouts. In the years since Levinson went missing, his family has released video and photos that they say prove he is alive. Hillary Clinton, while serving as U.S. secretary of state, said in 2011 that the State Department had received “indications” that Levinson was being held in South Asia.

CNN’s Carol Costello, Michael Martinez, Ray Sanchez and Joshua Berlinger contributed to this report.