A prominent American anchorwoman on Iranian state television's English-language service has been arrested by the FBI after flying into the U.S., the broadcaster reported Wednesday. The FBI did not immediately respond to requests for comment. The reported detention of Press TV's Marzieh Hashemi, born Melanie Franklin of New Orleans, comes as Iran faces increasing criticism of its own arrests of dual nationals and others with Western ties, previously used as bargaining chips in negotiations with world powers. Iran's state broadcaster held a news conference and launched a hashtag campaign for Hashemi, using the same techniques families with loved ones held in the Islamic Republic use to highlight their cases. 'We will not spare any legal action' to help her, said Paiman Jebeli, deputy chief of Iran's state IRIB broadcaster. Press TV said Hashemi, who has worked at the state broadcaster service for 25 years, had been arrested after arriving at St. Louis Lambert International Airport on Sunday. Jebeli alleged that her son, Reza Hashemi, had been arrested as well. Lambert Airport spokesman Jeff Lea declined comment, referring questions to the FBI. He said he could not confirm what flight Hashemi arrived on or when. St. Louis police said they were not involved. Rebecca Wu, St. Louis' FBI spokeswoman, directed questions to the press office at FBI headquarters. FBI headquarters in Washington did not respond to requests for comment. There were no references to any case against Hashemi in U.S. federal courts, nor in Missouri. Press TV said Hashemi had traveled to the U.S. 'to visit her family members, including her brother, who is suffering from cancer.' The broadcaster said she was a grandmother and aired footage of her anchoring news programs and talking about her experience as a reporter discussing the yearslong war in Syria, set to dramatic music. 'Unfortunately, because of the job that we do, here at Press TV and our position, there have been many stories that have been very, very difficult, very heavy,' she said. Hashemi describes herself online as having studied journalism at Louisiana State University in Baton Rouge. She converted to Islam in 1982 at age 22 after meeting Iranian activist students in Denver. Hashemi's brother, Milton Leroy Franklin of Metairie, a New Orleans suburb, told The Associated Press he knows only what his niece has put on Facebook. He said he believed his sister had been in custody since Sunday. 'We don't have any detailed information except she's being held. And her son is being held in a hotel in (Washington) and she's being held in some form of prison or incarcerated area,' Franklin said. 'I'm very concerned. There's no way of getting any word to her and she can't send any out, apparently. We're all in the dark and just waiting and praying that they release her.' He said she had visited to help plan a family reunion. 'We all got together, a small celebration, and prepared for the next time she would come,' Franklin said. 'They detained her on her way back home, from what I understand. We're looking to find out more.' Milton Franklin said his sister lives about half the time in Colorado, where her children live, and half the time in Iran. She married Hossein Hashemi, whom she had met while in journalism school at LSU; they had two sons and a daughter, Franklin said. He said her husband is dead. His sister remains an American citizen. Last week, Iran confirmed it is holding U.S. Navy veteran Michael R. White at a prison in the country, making him the first American known to be detained under President Donald Trump's administration. Iranian Foreign Ministry spokesman Bahram Ghasemi told state TV that Hashemi's arrest indicates the 'apartheid and racist policy' of the Trump administration. 'We hope that the innocent person will be released without any condition,' Ghasemi said. There are four other known American citizens being held in Iran, including Iranian-American Siamak Namazi and his 82-year-old father Baquer, both serving 10-year sentences on espionage charges. Iranian-American art dealer Karan Vafadari and his Iranian wife, Afarin Neyssari, received 27-year and 16-year prison sentences respectively. Chinese-American graduate student Xiyue Wang was sentenced to 10 year in prison. Also in an Iranian prison is Nizar Zakka, a U.S. permanent resident from Lebanon who advocated for internet freedom and has done work for the U.S. government. He was sentenced to 10 years on espionage-related charges. Former FBI agent Robert Levinson, who vanished in Iran in 2007 while on an unauthorized CIA mission, remains missing as well. Iran says that Levinson is not in the country and that it has no further information about him, though his family holds Tehran responsible for his disappearance. Tehran now says it has no information about him. ___ Associated Press writers Jim Salter in St. Louis, Janet McConnaughey in New Orleans, Heather Hollingsworth in Kansas City and Jon Gambrell in Dubai, United Arab Emirates, contributed to this report.