On Friday, the Islamic State claimed that the 26-year-old aid worker died in a Jordanian airstrike.
But White House spokesman Josh Earnest says there was no evidence that civilians were in the target area ahead of the strike.
Earnest says that Mueller’s parents received a private message over the weekend from her Islamic State captors. He says it included additional information about her death that they shared with the intelligence community, which concluded she had been killed.
Carl and Marsha Mueller, the parents of Kayla Jean Mueller, asked the Islamic State group to contact them privately, according to a statement released by a family representative. Prior to the news of their daughter’s death, Kayla’s parents directed a message to “those in positions of responsibility for holding Kayla,” they said: “You told us that you treated Kayla as your guest, as your guest her safety and well-being remains your responsibility.”
Mueller was the last-known American hostage held by Islamic State, which controls wide areas of Syria and Iraq. The militant Islamist group has beheaded three other Americans, two Britons and two Japanese hostages – most of them aid workers or journalists – in recent months.