DUBAI/WASHINGTON (Reuters) - 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 U.S. 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 a judge’s orders 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 U.S. District Court Judge Beryl Howell.

Hashemi’s detention added to the tense relations that have flared between Iran and the United States since U.S. 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.

She later called for demonstrations scheduled to demand her release to go ahead.

“I condemn the situation in the United States that individuals can be detained, arrested, without charge,” Hashemi said in a video posted on Press TV’s website.

“My request is that these demonstrations continue ... because it is not about me. It is important to know that this can happen to any person at any time in the United States - these illegal detentions, though they may call it legal,” she said.

U.S. 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 U.S. government has declined to disclose details of the criminal case in which Hashemi testified. However, a U.S. 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 Iran in the past few years on charges such as espionage and collaborating with hostile governments.