Kayla Mueller, a US humanitarian worker killed while being held by ISIS militants in August 2013, was reportedly repeatedly raped and tortured by the leader of the militant group - Abu Bakr al-Baghdadi - during her 18 months of captivity in Syria, US government officials said in a statement on Friday.
US officials told Mueller’s parents - Carl and Marsha Mueller - that their 26 year old daughter had been exposed to continuous physical and sexual abuse by Baghdadi during her captivity, family spokeswoman Emily Lenzner told Reuters by telephone.
"We can confirm that the Mueller family learned in June of Kayla's treatment from the FBI," Lenzner said.
Anonymous US officials released reports addressing Mueller’s suffering on Friday. ABC News subsequently was the first outlet to publish the reports on the same day.
The US government told Mueller’s parents that their daughter “was the property of Baghdadi,” the media organisation reported.
Baghdadi personally brought Mueller to be imprisoned in the home of Abu Sayyaf, a senior Tunisian ISIS leader in charge of oil and gas revenue for the group's operations in Syria, US counter-terrorism officials told ABC.
"Baghdadi was at the house of Sayyaf. He delivered Kayla Mueller, live and in person," one of several counter-terrorism officials briefed on the case told ABC.
The information about what likely happened to Mueller was revealed from multiple sources including US interviews with at least two teenage Yazidi girls who were held as "slaves" under the authority of Abu Sayyaf and a US interrogation of Sayyaf’s wife after she was captured by US forces following a raid in May which killed her husband, officials told ABC News.
There were rumors - now said to be false - from some US officials that Mueller had cooperated or was "a willing spouse."
The speculation was based on a smuggled written letter released by her family which Mueller wrote about a year into her captivity, in which she said she was "completely unharmed and healthy; I have been treated with the utmost respect and kindness."
Mueller’s parents were informed of their daughter’s status in captivity during a meeting in Washington, Lezner said, though she was not clear on whether Baghdadi was the person responsible for her abuse.
Mueller's family declined to comment on Friday regarding the latest statements concerning the treatment of their daughter.
"The family is so exhausted at this point, they need some time," Lenzner said.
ISIS claimed in February that Mueller’s death was cause by an air strike from a Jordanian fighter jet which struck the building where she was being held in outside Raqqa, the group's self-proclaimed capital in Syria.
But Jordan, along with several US officials, has expressed great doubts about ISIS’ account of her death as she had been held hostage for 18 months by that time.
Mueller was captured by ISIS in August 2013 while leaving a hospital where she had been working in Aleppo in northern Syria.
Before moving to Syria she went to Turkey in December 2012 to assist in providing humanitarian aid to Syrian refugees along the border.
ISIS has beheaded numerous hostages since 2013, including three Americans: James Foley, Steven Sotloff and Austin Bennett Tice.