DUBAI/WASHINGTON - An American-born anchor for Iran's state-run Press TV was freed after 10 days of detention in the United States after testifying as a material witness in an undisclosed federal investigation, a US federal court order said on Thursday.

Marzieh Hashemi testified four times before a federal grand jury beginning on Jan 18, according to the order, which made a partial disclosure of information in the case. She was released on Tuesday on orders of a judge and made her final grand jury appearance on Wednesday, it said.

Hashemi satisfied "her obligations in this material-witness matter, which is now closed," said the order signed by US District Court Judge Beryl Howell.

Hashemi's detention added to the tense relations that have flared between Iran and the United States since US President Donald Trump’s decision last May to pull out of an international nuclear deal and reimpose sanctions on Tehran.

Hashemi's release was first reported by Press TV, which quoted a statement by her family.

"They (the family) still have serious grievances and they want assurances that this won’t happen to any Muslim – or any other person – ever again," Press TV said.

Hashemi, 59, was arrested by the FBI at St. Louis Lambert International Airport and transferred to a detention center in Washington D.C., where she was held for two days before managing to contact her family, Press TV said.

US federal law allows the government to arrest and detain a witness if it can prove their testimony is material to a criminal proceeding and it cannot guarantee their presence through a subpoena.

The US government has declined to disclose details of the criminal case in which Hashemi testified. But a US government source told Reuters it appeared that the grand jury was examining whether English-language Press TV is a propaganda outlet that failed to register with the Justice Department as an agent of a foreign government.

Hashemi was born Melanie Franklin in the United States and changed her name after converting to Islam. She received Iranian citizenship after marrying an Iranian. She had traveled to the United States to visit her family, Press TV said.

Several Iranian dual nationals from Austria, Britain, Canada, France and the United States have been detained in the past few years in Iran on charges such as espionage and collaborating with hostile governments.

Reuters