Press TV said Marziyeh Hashemi was arrested at St. Louis Lambert International Airport on Sunday and was sent to custody in Washington DC, but no formal charges have been made against her.
Federal Bureau of Investigation (FBI) officials were not immediately available for comment.
Hashemi was in the United States to visit her family, the broadcaster said, and was allowed to call her daughter two days after her arrest.
According to Press TV, Hashemi was born as Melanie Franklin in the United States, and changed her name after converting to Islam.
She was quoted as saying by Press TV that she had been prevented from observing the Islamic dress code, hijab, in prison, and she was only offered pork as a meal, which is prohibited in Islam.
The only food she has had over the past two days has been a “packet of crackers,” Hashemi was quoted as saying by Press TV.
Reuters could not independently verify this account of her treatment.