Kayla Mueller, 26, an American humanitarian worker from Prescott, Arizona is pictured in this undated handout photo obtained by Reuters February 6, 2015. U.S. President Barack Obama on February 10, 2015 confirmed the death of Mueller, a U.S. aid worker who had been held hostage by Islamic State militants. Kayla Mueller was abducted in Aleppo, Syria in August 2013. Mueller Family/Handout via Reuters (Handout/Reuters)

Federal prosecutors are preparing criminal charges against an Iraqi woman suspected of taking an American aid worker as a hostage of the Islamic State terrorist group in Syria, U.S. officials said.

But officials cautioned that her possible relocation to the United States is uncertain because the Iraqi government could object to her extradition and seek to put her on trial.

The woman, known as Umm Sayyaf, is currently in U.S. military custody in Iraq, where an interrogation team from the CIA, FBI and Pentagon has questioned her for intelligence purposes, officials said.

Umm Sayyaf was detained after Delta Force commandos assaulted a compound in eastern Syria in May, killing her husband, Fathi ben Awn ben Jildi Murad al-Tunisi, a Tunisian man known as Abu Sayyaf who was suspected of overseeing the Islamic State’s illicit oil and gas operations.

After her capture in Syria, she was taken to a U.S. base near the Iraqi Kurdish city of Irbil.

In this May 30, 2013, photo, Kayla Mueller is shown after speaking to a group in Prescott, Ariz. The parents of an American woman held by Islamic State militants say they have been notified of her death. Carl and Marsha Mueller, the parents of Kayla Jean Mueller, released a statement on Tuesday saying they have been told that she has died. The White House also issued a statement confirming her death.The Islamic State group said Friday that the 26-year-old Mueller from Prescott, Arizona, died in a Jordanian airstrike. (AP Photo/The Daily Courier, Matt Hinshaw) (Matt Hinshaw/AP)

Officials said Umm Sayyaf could be charged with providing material support to a foreign terrorist organization and conspiracy to commit hostage-taking — a count that can carry the death penalty.

Kayla Mueller, 26, an American woman from Prescott, Ariz., was held by Umm Sayyaf for months and repeatedly abused while in captivity, according to U.S. intelligence officials.

The Islamic State claimed that Mueller was killed this year after a Jordanian fighter plane dropped a bomb on the house where she was being kept. The U.S. government confirmed the death but not the cause. Mueller was abducted in August 2013 after leaving a hospital in the Syrian city of Aleppo.

A prosecution of Umm Sayyaf for her suspected role in taking Mueller hostage would be the first publicly known FBI case involving an alleged senior figure in the Islamic State. The FBI has faced harsh criticism from families of those abducted in Syria, and officials said the bureau is eager to demonstrate its ability to extradite and punish those responsible for seizing Mueller and other Americans.

Officials said agents with the FBI’s Washington Field Office are investigating Mueller’s case. An FBI spokesman declined to comment. A spokesman for the Justice Department’s National Security Division, Marc Raimondi, said no decision has been made yet on what to do with Umm Sayyaf.

“While I have no comment on the specific stage the process is in, we are working to determine an ultimate disposition for the detainee that best supports the national security of the United States and of our allies and partners,” Raimondi said.

The Obama administration has not hinted whether the government of Iraqi Prime Minister Haider al-Abadi would object to having an Iraqi citizen, held on Iraqi soil, tried in a foreign court. The Iraqi ambassador to the United States, Lukman Faily, declined to discuss Umm Sayyaf’s case.

Although she is in U.S. custody in Iraq, former officials said it is unlikely that the United States would move her without permission from Baghdad. “Most countries won’t extradite their own citizens,” said a former senior FBI official. “This is probably a long shot.”

If a prosecution moves forward with the blessing of the Iraqi government, U.S. Attorney General Loretta E. Lynch would decide where the case is prosecuted. Officials said a U.S. attorney office in New York, Virginia or the District would likely handle the case.

At the time of Umm Sayyaf’s capture, the charge of material support for terrorism carried a maximum sentence of 15 years in prison. It has recently been increased to 20 years with the passage of the USA Freedom Act.

Bobby Chesney, who specializes in national security law at the University of Texas, said the United States is unlikely to seek extradition of Umm Sayyaf unless it plans to pursue additional charges with more severe penalties. If convicted of a conspiracy to take a hostage, Umm Sayyaf could face life in prison or the death penalty because Mueller died while in the hands of her captors.

If the United States turns Umm Sayyaf over to the Iraqis, “there won’t be any trouble getting a conviction,” Chesney said. “So why bring her unless there is a special interest.”

It’s not clear whether Umm Sayyaf has already been advised of her right to remain silent, known as a Miranda warning. Citing the pattern of other recent cases in which accused terrorists were apprehended overseas, U.S. officials said it is likely that she has already been issued a Miranda warning and questioned by a second set of FBI agents known as a “clean team.”

Such teams are sent to conduct follow-on interviews that can be used by prosecutors. Information gathered by the high-value interrogation group — which was created by President Obama to replace a controversial CIA program set up after the Sept. 11, 2001, attacks — is inadmissable in court.

“If they talk for an intelligence interview, they’re usually willing to keep talking” after being read their Miranda rights, a U.S. official said. That would enable the FBI to get much of the same information as that obtained by the first interrogators.

Terrorism suspects captured in Libya in 2013 and 2014 were read their Miranda rights within about a week while held on U.S. warships.

Former and current Justice Department officials say the Umm Sayyaf case could be problematic, in part because prosecutors would have to demonstrate that she was a willing participant in the abduction and not under duress.

Mueller had traveled to the region in late 2012 to help refugees trying to escape the civil war in Syria. After she was abducted, her case was kept from public view in hopes that she would be released.

Instead, she was killed in February 2015. U.S. intelligence officials said they are still trying to determine exactly how she died. The Islamic State beheaded American journalists James Foley and Steven Sotloff, as well as former U.S. soldier Abdul-Rahman Kassig, previously known as Peter Kassig.

Missy Ryan and Greg Miller contributed to this report.