The U.S. government scrambled Friday to confirm the self-proclaimed Islamic State claim that its last remaining American hostage, a young woman and humanitarian aid worker, was killed by a Jordanian airstrike.

So far, three U.S. government officials told The Daily Beast they have no evidence either that she was killed or remains alive.

In the claim, published by the private intelligence group SITE on Friday, ISIS released the name of the hostage, Kayla Mueller, as well as what it claimed were personal details about her, including her phone number. The group showed no photos of her.

Rather it showed the crumbled building where she was allegedly held, saying it was somewhere near Raqqa, the group’s Syrian capital. U.S. military officials said they were doing battlefield assessments with that photo to determine whether it was destroyed by a coalition strike, and if so, when. They so far do not believe it was a Jordanian strike. Jordan ramped up its efforts since Tuesday when ISIS released a video showing the group gruesome burning to death of Jordanian Lt. Moaz al-Kasesbeh. But Jordan has not struck inside Raqqa since al-Kasesbeh’s death but areas east, U.S. military officials told The Daily Beast.

A Jordanian official denied ISIS’s claims that Mueller was killed in one of the country’s airstrikes. “This is just another PR stunt,” the official told The Daily Beast. “This is just part of their whole media-spinning strategy. They’re trying to throw a wedge in the coalition” to combat ISIS. The official noted that ISIS has manipulated the public before when it comes to the status of hostages, most recently by seeming to claim that the Jordanian pilot was alive when he’d really been killed weeks ago.

“There is no clear indication that she is dead or alive," said a U.S. national-security official familiar with the search for Mueller. “If she is dead, why aren't they showing her corpse? They've done it before with everybody else. Why is the news media not calling them out?”

This official said ISIS's claim changed nothing has changed from the U.S. perspective.

“Just because it is on CNN doesn't mean we're gong to look harder,” the official added. “A U.S. person is being held against their will by an enemy. Every effort that can be made is being made. It is the top priority. It has been a priority since it happened.”

“We are obviously deeply concerned by these reports. We have not at this time seen any evidence that corroborates ISIL’s claim,” said Bernadette Meehan, a spokesperson for the National Security Council, using an alternate acronym for the extremist group.

Mueller, a 26-year-old from Arizona, was taken captive by ISIS on August 4, 2013, in Aleppo, Syria, while leaving a Spanish Doctors without Borders hospital.

The Daily Beast, along with other news organizations, had agreed to withhold Mueller’s name at the request of her family and U.S. officials, who feared that further attention would put her in jeopardy.

If confirmed, Mueller’s death would bring to an end months of speculation about what ISIS, whose brutality seems to know no bounds, had planned for its last American captive. ISIS has killed Muslim women, as well as children. And the group has held other female captives, notably Yazidi women for example. But Western women had, so far, not been touched.

That fact, terrorism analysts had said, may have helped to keep Mueller alive. Even for a group as brutal as ISIS, killing a woman aid worker could potentially be seen as a bridge too far, and risk igniting public opposition to the group, which aims to establish a new caliphate.

But since the U.S-led campaign began Aug. 8, there were increased concerns for her safety. Indeed, Pentagon officials privately fretted that ISIS would claim hostages or civilians had been killed by their strikes. As it turned out, ISIS wants to shift all attention away from the strikes. After nearly 4,000 targets hit, this appears to be the first time ISIS has claimed coalition forces killed a captive.

In response to al-Kasesbeh’s death, the Jordanian government carried out a death sentence against two al Qeada operatives the next day. Among them was a 44-year-old woman named Sajida al-Rishawi, a would be suicide bomber in the 2005 attack on three Jordanian hotels. The death of a jihadist woman heralded by some ISIS supporters as a hero may have led to a tit-for-tat response by ISIS, the death a Western female hostage, by the Jordanians no less.

Mueller had said she felt drawn to humanitarian work to ease the suffering Syrians, particularly children, whose lives were devastated by years of civil war. Working in refugee camps in Turkey with the humanitarian group Support to Life, she used art as therapy, encouraging children to draw pictures of places where they felt safe—invariably they drew their houses, which they’d had to flee or were destroyed.

“When Syrians hear I’m an American, they ask, ‘Where is the world?’ All I can do is cry with them, because I don’t know,” she said during a speech to the Kiwanis Club in Prescott, Arizona, her hometown, in 2013.

“In the chaos of waking up in the middle of the night and being shelled, we’re hearing of more children being separated from their families by accident,” Mueller said. She told the audience she felt she “can’t do enough” to help Syrian refugees and others fighting the dictatorship of Syrian strongman Bashar al-Assad.

The Daily Courier reported on the speech and recounted how while working in Turkey, Mueller helped to reunite a Syrian man with a young family member after his camp was bombed. Mueller used a video image of the missing boy to track him down at a hospital after he came out of surgery.

In her speech, Mueller evinced a passion for helping the Syrian people and was hopeful that her work would make a difference in their suffering.

“For as long as I live, I will not let this suffering be normal. I will not let this be something we just accept. It’s important to stop and realize what we have, why we have it and how privileged we are. And from that place, start caring and get a lot done.”

Mueller graduated from Northern Arizona University in 2009. From then until 2011, she lived and worked with humanitarian aid groups in northern India, Israel, and the Palestinian territories. She then returned home to Arizona and worked for a year at an HIV/AIDS clinic and volunteered nights at a women's shelter.

In December 2011, Mueller traveled to France to work as an au pair so she could learn French and then working in Africa. But in December 2012, she went to the Turkish and Syrian border and worked with aid groups helping Syrian refugees.

Mueller's kidnappers first made contact with her family in May 2014, providing proof of life evidence that she was alive and demanding a ransom.

Notably, Mueller didn’t appear in any ISIS videos, including at the end of one released in November 2014 documenting the death of Peter Kassig, another aid worker who, at the time, was the only other American the group was holding.

With the Kassig video, ISIS broke with its custom of showing the next hostage it intends to kill. Subsequent ISIS films showed the murder of a group of Syrian pilots, and most recently the beheading of two Japanese men and the burning alive of the Jordanian pilot.

After Kassig was shown dead, a former U.S. counterterrorism official told The Daily Beast that before ISIS decided what to do with its remaining American hostage, it would consider carefully the public reaction it could spark. “Before they’re doing anything, they want to have a really good feel for how it will play,” the former official said.

As recently as Wednesday, the State Department said it was doing all it could to bring the woman home. At an event about the U.S. policy toward hostage cases, Douglas Frantz, U.S. assistant secretary of State for public affairs, said the case was a priority.

“We are working very hard,” Frantz told the audience at the Newseum in Washington D.C., “to free an aid worker who is held in Syria.”

-- with additional reporting by Kevin Maurer