The family of an American woman held hostage by Isis have been told she is dead, the White House has confirmed.
On Friday, the jihadist group claimed that Kayla Jean Mueller had been killed during a Jordanian air strike, although that is yet to be confirmed. She was taken in August 2013 while leaving a hospital in Syria.
A native of Prescott, Arizona, Mueller reportedly demonstrated an interest in aid and human rights work during her high school years, as a member of the Save Darfur Coalition. She graduated from Northern Arizona University in Flagstaff in 2009 and afterwards worked at an orphanage in India, and at an HIV/AIDS clinic at home in the US.
She had volunteered for schools and aid organisations in both Israel and the West Bank, and in Dharamsala, India, where she taught English to Tibetan refugees. According to the Washington Post, in 2012 Mueller began working with victims of the conflict in Syria for the humanitarian group Support to Life.
She disappeared after driving into the norther Syria city of Aleppo with her Syrian boyfriend and was captured along with several other aid workers in August 2013 while working at a hospital in Aleppo.
Her colleagues received subsequently received a proof-of-life video, showing her wearing a hijab and begging for her life.
A year later, CBS News reported that Isis had demanded a ransom equivalent to £4.3m for her release.
In pictures: Anti-Isis protests in Jordan
In pictures: Anti-Isis protests in Jordan
1/15 Amman, Jordan
Members of Jordan's Al Assaf tribe burn a ''Wanted Dead'' poster of Islamic State leader Abu Bakr al Baghdadi at a rally
2/15 Amman, Jordan
Jordanian protesters carry an effigy of leader of the militant Islamic State Abu Bakr al-Baghdadi, during a march after Friday prayers in downtown Amman
3/15 Amman, Jordan
Jordanian Queen Rania (C) holds a placard during a demonstration to express solidarity with the pilot murdered by the Islamic State
4/15 Amman, Jordan
A protester dressed in a Jordanian flag joins others as they hold up pictures of Jordanian King Abdullah and Jordanian pilot Muath al-Kasaesbeh, while chanting slogans during a march against Islamic State
5/15 Amman, Jordan
Jordanians hold banners shouting slogans during a demonstration to express their solidarity with the pilot murdered by the Islamic State
6/15 Amman, Jordan
Jordanians carry banners and pictures of executed Jordanian pilot Muath al-Kassasbeh while shouting slogans against the group calling themselves the Islamic State, during a march after noon pray in downtown Amman
7/15 Amman, Jordan
Protesters hold up pictures of Jordan's King Abdullah and pilot Muath al-Kasaesbeh as they chant slogans during a rally in Amman to show their loyalty to the King and against the Islamic State
8/15 Amman, Jordan
Jordanians chant slogans to show their support for the government against terror during a rally
9/15 Amman, Jordan
Jawdat al-Kaseasbeh, a brother of slain Jordanians pilot Muath al-Kaseasbeh, reacts to people gathering to show their support for the government against terror during a rally
10/15 Amman, Jordan
A Jordanian protester kisses a poster bearing the image of Jordanian pilot Muath al-Kasaesbeh during a rally to show their loyalty to King Abdullah and against the Islamic State
11/15 Amman, Jordan
A Jordanian shouts slogans during a rally against the Islamic state group and in reaction to the burning alive of Jordanian pilot Maaz al-Kassasbeh by the group's militants
12/15 Amman, Jordan
Jordanians carry pictures of pilot Maaz al-Kassasbeh at a protest against Islamic State
13/15 Amman, Jordan
Supporters and family members of Jordanian pilot Lt. Muath al-Kaseasbeh express their anger at his murder at the tribal gathering chamber in Amman, Jordan
14/15 Aye Village, Karak, Jordan
The King of Jordan, Abdullah II (L), embracing Safi al-Kassasbeh (R), the father of the recently executed Jordanian pilot
15/15 Aye Village, Karak, Jordan
Jordan's Queen Rania offers her condolences to the family of Jordanian pilot Muath al-Kasaesbeh, at their family home of Muath
REUTERS/Petra News Agency
Her identity was never disclosed by authorities out of concern for her safety when she was taken hostage.
In 2013, Mueller spoke about her experiences to the Prescott Kiwanis Club, a volunteer group of which her father Carl is a member. “Syrians are dying by the thousands, and they're fighting just to talk about the rights we have,” she said.
“For as long as I live, I will not let this suffering be normal, something we just accept... It’s important to stop and realise what we have, why we have it and how privileged we are. And from that place, start caring and get a lot done.”
"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.
A statement from her family's representative said: "The suffering of the Syrian refugees drew Kayla to the Turkish/Syrian border... to assist families who had been forced to flee their homes.
"Kayla found this work heartbreaking but compelling; she is extremely devoted to the people of Syria.
"The common thread of Kayla's life has been her quiet leadership and strong desire to serve others.
"When asked what kept her going in her mission, she said: 'I find God in the sufferng eyes reflected in mine. If this is how you are revealed to me, this is how I will forever seek you.'"