Red Cross officials have revealed why they have "high degree of confidence" missing Kiwi woman Louisa Akavi is still alive.
Akavi was kidnapped by Islamic State fighters in Syria in 2013, while seconded to the International Committee of the Red Cross (ICRC). The veteran nurse was on her 17th international field mission providing humanitarian aid.
Her case has been kept secret, officials from the Red Cross and the Government afraid bringing attention to her case would end in her execution.
"Our number one priority all along has been Louisa's safety, and decisions have been taken always with that in mind," NZ Red Cross secretary general Niamh Lawless said on Monday, after making Akavi's case public.
"One of those decisions was to keep the information as far out of the public eye as possible."
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The most recent "plausible" sighting of Akavi was in December, near Baghouz in the war-torn country's southwest.
"It looks like she has been able to continue providing medical care, because that's her medical oath," said Lawless. "As a humanitarian working in a neutral way, that's what she would do."
Lawless wouldn't comment on who she might have been treating - rebels, Syrian fighters, civilians or even Islamic State militants.
"We know that as a humanitarian, that's what she would do. She's dedicated her whole life to providing need to the most vulnerable in a neutral and impartial way."
NZ Red Cross board member John Dyer said they have a high degree of confidence the woman spotted in December was Akavi.
"It was information that we received as part of our operational briefings. The people that relayed that information were confident that it was her."
The ICRC didn't go public with her story then because at that point, Islamic State was still a military force to be reckoned with. It's since been wiped out territorially, though perhaps not ideologically.
"In the last few months, the situation over there has been ... dynamic, it's fluid and uncertain," said Dyer.
"Those leads were followed up at that time, but realistically, it was generally felt that we wouldn't secure any further information at that time. That's why it was better to continue with what was happening, to find out more using people on the ground, operation people, and leave it at that."
The collapse of the brutal caliphate has prompted ICRC to try a new approach finding Akavi, one of the last Western hostages captured by IS still to be accounted for.
Dyer said the quiet approach is usually the best, but situations can change rapidly.
"Generally speaking, the approach that's taken is that in order to enable discussions to go on behind the scenes, it is better to try and keep the situation quiet and not make it public. There has been significant work done behind the scenes, and this has enabled some information to come out - ICRC has the operational lead, they have vast experience in this.
"There's always a risk [going public might not work]. There's no such thing as zero risk as such, but a decision was taken to try and seek further information."
Lawless said there was "no right or wrong time" to go public.
"We call on whoever is holding Louisa to release her immediately and unconditionally, and for anyone with information to come forward."