WASHINGTON (AP) — The son of an American-born anchor for Iran’s state television broadcaster says his mother will appear before a U.S. grand jury.

Hossein Hashemi tells The Associated Press that his mother, Marzieh Hashemi, is being taken to court in Washington, D.C., on Friday.

He has said Marzieh Hashemi was taken into custody by federal agents on Sunday in St. Louis and then was transferred to Washington. He has said she’s been jailed as a material witness, though it’s unclear for which case.

She hasn’t been charged with a crime.

Federal law allows judges to order a witness to be arrested and detained if the government can prove his or her testimony has extraordinary value for a criminal case and he or she would be a flight risk and unlikely to respond to a subpoena.