Reporters Without Borders (RSF) has condemned the "opaqueness" surrounding the detention of a U.S.-born Iranian television anchor in the United States, and called on U.S. authorities to guarantee the journalist's fundamental rights.
"The U.S. judicial authorities must announce the charges they plan to bring" against Marzieh Hashemi, the Paris-based media watchdog said on January 21.
Hashemi works for Iran's state-run English-language Press TV news channel.
Her son has said she was detained by federal agents on January 13 in St. Louis, Missouri, where she had filmed a Black Lives Matter documentary.
She was then transported to Washington and has been in custody since then.
According to federal court documents made public on January 18, Hashemi was detained as a material witness, though it is unclear for which case.
Officials said she was expected to be released immediately after her testimony is completed, but it's not clear when that would be.
Iran has called for Hashemi's immediate release.
"The US govt needs to explain how Marzieh Hasehmi -- a journalist and grandmother -- is such a flight risk that she must be incarcerated until she finished her testimony to a grand jury," Foreign Minister Mohammad Javad Zarif tweeted on January 21.
The Reuters news agency had quoted a U.S. government source as saying it appeared that a grand jury was examining whether Press TV is a propaganda outlet that failed to register with the Justice Department as an agent of a foreign government.
The FBI and Justice Department have not commented publicly on Hashemi's case.
Hashemi appeared in court on January 18, according to Iranian state broadcaster IRIB, and a second hearing was scheduled for January 23.
Press TV has said that Hashemi was born Melanie Franklin in the United States and changed her name after converting to Islam.
Iranian officials have said that Hashemi received Iranian citizenship after marrying an Iranian.