An American woman taken hostage by the self-declared Islamic State has died after Jordanian warplanes attacked the building where she was being held in Syria, the extremist group says.

The claim was announced on Twitter and reported by the SITE Intelligence Group, which monitors jihadi activity. NPR is working to determine the facts of the story.

Update at 1:25 p.m. ET: Hostage's Name Confirmed By Family

We do not have confirmation of her fate, but her family says the American hostage is Kayla Mueller, an aid worker from Prescott, Ariz., who was taken captive on Aug. 4, 2013, as she left a Doctors Without Borders hospital in Aleppo.

Mueller was identified as the American hostage in the ISIS release Friday.

In a statement provided to NPR's Martin Kaste, the family describes Mueller, 26, as someone who was repeatedly recognized for her academic abilities and her commitment to philanthropy. She was named a National Young Leader; she also received the President's Award for Academic Excellence in 2007.

From the family's statement:

"Kayla has spent her adult life traveling the world and helping those in need. After graduating from college, she spent more than one year living and working with humanitarian aid groups in northern India, Israel and Palestine. She returned home to Arizona in 2011, and worked for one year at an HIV/AIDS clinic while volunteering at a women's shelter at night. In December 2011, she traveled to France to be an au pair so she could learn French in preparation for work in Africa.

"War sidetracked Kayla's Africa plans as she was drawn to alleviate the suffering of Syrian refugees. She moved to the Turkish/Syrian border in December 2012 and began working with the organizations Support to Life and the Danish Refugee Council to assist families who had been forced to flee their homes. Kayla found this work heartbreaking but compelling; she was extremely devoted to the people of Syria."

Mueller was taken captive along with three others; her family says the other hostages were released in subsequent months.

Our original post continues:

The ISIS statement reads in part:

"The criminal Crusader coalition aircraft bombarded a site outside the city of Raqqah today at noon while the people were performing the Friday prayer. The air assaults were continuous on the same location for more than an hour.

"Allah made their pursuit disappointed and deterred their cunning, and no Mujahid was injured in the bombardment."

Photos released along with the ISIS statement show a multistory building in different states of destruction; the final image shows it essentially reduced to rubble.

"We are obviously deeply concerned by these reports," said State Department spokeswoman Jen Psaki, after the U.S. agency initially declined to comment. "We have not at this time seen any evidence that corroborates ISIL's claim."

As we've reported, Jordan has stepped up its airstrikes on ISIS following the group's brutal killing of a captured pilot.

Late Friday, Jordan called the ISIS claim a "PR stunt" that is meant to "drive a wedge between the coalition" members fighting the group, as NPR's Alison Meuse reports.

"They tried to cause problems internally in Jordan and haven't succeeded," said Jordanian Interior Minister Hussein Majali. "They are now trying to drive a wedge between the coalition with this latest low PR stunt."

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