The International Committee of the Red Cross (ICRC) has appealed for information on the fate of three employees abducted in Syria more than five years ago and last known to have been held by Islamic State.
Breaking its silence on the case on Sunday, the independent aid agency identified the three as Louisa Akavi, a nurse from New Zealand, and Syrian drivers Alaa Rajab and Nabil Bakdounes.
"Our latest credible information indicates that Louisa was alive in late 2018," it said.
U.S.-backed forces proclaimed the capture of Islamic State's last territory in Syria last month, eliminating its rule over a caliphate it had proclaimed in Iraq and Syria in 2014.
ICRC officials said Akavi might have been swept up among some 70,000 women and children who fled to al-Hol camp after the fall of Islamic State, many of them jihadist sympathisers.
ICRC President Peter Maurer raised her case during a visit to the camp, run by Kurdish-led Syrian Democratic Forces (SDF), in March, they added.
"We call on anyone with information to please come forward. If our colleagues are still being held, we call for their immediate and unconditional release," the ICRC said in a statement providing a Syrian contact number: +963 953 555 745.
It said it had not been able to learn more details about the two drivers, and their fate was not known.
The three were travelling in a Red Cross convoy in October 2013, delivering supplies to medical facilities in Idlib, northwestern Syria, when it was stopped by armed men. Four other people abducted with them were released the next day.
The Swiss-run agency has a policy of never paying ransoms.
Akavi, now 62, joined the ICRC in 1988 and has worked in a number of hotspots.
She has been held longer than anyone in ICRC's 156-year history, said Dominik Stillhart, ICRC director of operations worldwide.
New Zealand's government said it was searching for Akavi. Foreign Minister Winston Peters said the government had deployed a non-combat team based in Iraq that included special operations personnel, "focused on locating ...and identifying opportunities to recover her."
After being moved by IS forces to Raqqa in 2017, Akavi was seen in Al-Bukamal in late 2018, close to the Syrian-Iraqi border, the last concrete information on her whereabouts, Stillhart said.
"What we actually know is that Louisa has been working as a nurse during her abduction which shows her dedication and commitment," he said.