Parents of 26-year-old Kayla Jean Mueller, an American aid worker held hostage by the Islamic State group since August 2013, said in a statement released late on Friday, that they are hopeful she is still alive, according to media reports. Militants affiliated to ISIS had claimed, earlier on Friday, that Kayla was killed during Jordanian airstrikes on the group’s stronghold in Raqqa, Syria.

“To those in positions of responsibility for holding Kayla; in adherence to your warnings and out of concern for Kayla's safety, we have been silent until now,” Carl and Marsha Mueller reportedly said in the statement. “After going to extraordinary efforts to keep Kayla's name out of the media for so long, by securing the cooperation of journalists throughout the world, her name was released today.”

Kayla’s parents urged the militants to contact them directly. “We have sent you a private message and ask that you respond to us privately. We know that you have read our previous communications; John Cantlie made references to them in October,” the Muellers said in the statement, referring to an earlier video released by ISIS featuring the British journalist held captive by ISIS.

Although ISIS had, on Friday, released a statement claiming that Kayla was killed when a “plane from the crusader coalition” bombed Raqqa, U.S. and Jordanian officials have so far not verified the reports.

When asked about the group’s claim of Kayla’s death, U.S. State Department Spokesperson Marie Harf said that U.S. authorities did not “have any way to corroborate this information.”

Jordanian authorities, meanwhile, alleged that the claim is a “PR stunt” by ISIS and that the group is trying to “drive a wedge between the coalition.”

“What we know about this terrorist organization is that they are liars when it comes to these things,” Jordanian government spokesman Mohammed al-Momani told CNN on Friday.

If Kayla’s death is confirmed, she would be the fourth American, after James FoleySteven Sotloff and Peter Kassig, to die while being held by ISIS. The group has also executed two British nationals -- David Haines and Alan Henning