The widow of a former ISIS leader was accused Monday of taking part in the abduction of Kayla Jean Mueller, the humanitarian aid worker from Arizona who was kidnapped in Syria in 2013 and died last year.
Federal prosecutors filed the charges against a 25-year-old Iraqi woman, Nisreen Assad Ibrahim Bahar, also known as Umm Sayyaf. She was married to Abu Sayyaf, a senior ISIS leader who was killed last May in a firefight with U.S. forces.
The Justice Department said she is in Iraqi custody for terrorism-related activities.
"We fully support the Iraqi prosecution of Sayyaf and will continue to work with the authorities there to pursue our shared goal of holding Sayyaf accountable for her crimes," said John Carlin, assistant attorney general in charge of the Justice Department's National Security Division.
"We will continue to pursue justice for Kayla and for all American victims of terrorism," he said.
Prosecutors said Umm Sayyaf threatened Mueller and two other women who were being held, "telling them she would kill them if they did not listen to her."
The FBI said in court documents filed in Alexandria, Virginia, that the captives were held in locked rooms, sometimes handcuffed, and that Mueller was sexually abused by ISIS leader Abu Bakr al-Baghdadi.
"Umm Sayyaf knew how Mueller was treated by Baghdadi when Mueller was held against her will in Sayyaf's home," prosecutors said.
The statement was the U.S. government's first official confirmation of the sexual abuse, which Mueller's family revealed last year.
Court documents filed Monday said Sayyaf and her husband "held young women who were sold or traded" to ISIS men.
The FBI said Umm Sayyaf was interviewed by FBI agents in Iraq in 2015. The agents said that she "admitted that her family belonged to al-Qaeda in Iraq" and that she took part in holding the women hostage on behalf of ISIS.
The agents said she told them that al-Baghdadi "owned" Mueller during the time of captivity at the Sayyaf home.
"The defendant admitted that 'owning' is equivalent to slavery," prosecutors said.
Mueller and another person traveled into northern Syria on Aug. 3, 2013. On their second full day in the country, they were kidnapped by ISIS soldiers. ISIS leaders notified the Mueller family of her death in an e-mail Feb. 7, 2015.