A black flag belonging to the Islamic State is seen near the Syrian town of Kobani, as pictured from the Turkish-Syrian border near the southeastern town of Suruc in Sanliurfa province, October 6, 2014.
A black flag belonging to the Islamic State is seen near the Syrian town of Kobani, as pictured from the Turkish-Syrian border near the southeastern town of Suruc in Sanliurfa province, October 6, 2014. REUTERS/Umit Bektas REUTERS/Umit Bektas

ISIS supporters have claimed that the U.S. aid worker held captive by militants was killed in a Jordanian airstrike. U.S. intelligence officials are currently investigating the alleged death of 26-year-old Kayla Mueller.

According to Fox News, Mueller, whose identity was previously withheld at the request of her family and the U.S. government, is believed to be the last American hostage ISIS has since the beheading of another aid worker, Peter Kassig, in November. A statement posted on a website used by ISIS fighters contained information that Mueller has been killed by a missile strike last week when Jordanian planes bombed Raqqa.

ISIS supporters said Mueller died when rockets partially destroyed the building where she was being held. Other ISIS fighters also died during the aerial assault, reports The Guardian. Several photos of the alleged building complex were shown in the statement. In response to Mueller’s reported death, National Security Council spokesperson Bernadette Meehan said authorities were concerned about the reports but revealed there was no evidence to support the claim.

Following the reported death, the Mueller family released a statement that they were still “hopeful” that Kayla is alive. The family addressed her captors and told them that they sent a private message. “We know that you have read our previous communications,” said the hostage’s family in the statement.

State Department deputy spokesperson Marie Harf said there was no confirmation about the validity of the report but revealed ISIS has a number of U.S. citizens being held hostage. Mueller was taken by ISIS militants last Aug. 2013 after leaving a hospital run in Aleppo.

Meanwhile, the size of ISIS’ army is reportedly bigger than what the CIA has previously thought. WND reports that ISIS and its allies have 180,000 fighters. According to an Egyptian intelligence document, ISIS has been working to build its own coalition of fighters while the U.S. was still gathering support for its own international coalition to counter the militants.

The document suggested that ISIS’ army is six times more than what the CIA had estimated last September 2014 when the intelligence agency thought the group had 20,000 to 30,000 fighters. An intelligence official in Egypt claimed that ISIS was creating the fundamentals of government outside of Iraq and Syria.

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