The Islamic State militant group claims that its last American hostage has been killed during a Jordanian air strike in its capital city. The CIA is currently investigating the claim, as ISIS offered no video or photo evidence.

SITE, a U.S. group that monitors terrorist activity, translated a report from ISIS that was posted on Twitter today that claims Kayla Mueller was killed. ISIS posted pictures of the bomb site in Raqqa in northern Syria. There were no pictures of a body or video that showed Mueller.

There has yet to be an independent confirmation of Mueller’s death, so sources told Fox News that the CIA is investigating.

Mueller was the last remaining American hostage ISIS was holding and will be the fourth American hostage to die just since August if her death is confirmed, notes The Washington Post. The Arizona native was kidnapped in August 2013 when she was helping Spanish Doctors Without Borders in Aleppo, Syria.

The FBI and her family had requested that the media not reveal her name, but White House Chief of Staff Denis McDonough let it slip during an ABC interview. President Obama told NBC on Sunday that the government was working to secure her release.

As USA Today notes, Jordan has been bombing ISIS-controlled areas for the past two days in response to the death of Lt. Muath al-Kaseasbeh.