One of the Papua New Guinean women being held hostage in the country's highlands has been freed, but the Australian professor remains captive.
PNG's Prime Minister James Marape has announced the release of the woman, while calling for the criminals to set free the remaining hostages.
The professor, who works for an Australian university and is a permanent resident but a New Zealand citizen, is still being held in remote bushland along with two other Papua New Guinean colleagues.
The academic team was doing fieldwork in a remote part of PNG's highlands near Mount Bosavi, on the borders of the Hela and Southern Highlands provinces, when they were taken.
The ABC understands the woman released on Wednesday is the program coordinator who was with the team.
'You have no place to hide'
Mr Marape said he had "a strong message" to the criminals involved.
"You have no place to hide," he said.
"Your names and your faces are being profiled as we speak – [already] we have 13 names and pictures," he said.
Police believe the gang that kidnapped the four are from Komo in Hela Province and were returning from the village of Kamusi when they came across the researchers.
The gang has demanded a ransom be paid for their release.
Mr Marape praised the work of the research team, and described the professor as a "friend of the country".
"They're not up there looking for money, they're working there to protect and promote our home up there in the Mountains of Bosavi as a rich biodiversity site and an archaeological site."
He called on the criminals to settle things the "Melanesian way".
"You want forgiveness? There is space for forgiveness if you release the [remaining] people.
"Once [they] are released there is always a place for pardon, power of mercy, forgiveness, the due process of law will take its course."
Remaining hostages being held in "difficult terrain"
PNG's Police Commissioner David Manning said he believed the remaining three hostages were "in reasonable health" but were "being held in difficult terrain".
"We are continuing to work to strengthen lines of communication, which remains a challenging aspect of this operation," he said.
Mr Manning said the priority remained on returning the remaining captives safely to their families.
"Negotiations are being undertaken with care so as to seek a peaceful resolution and minimise an escalation of tensions.
"That being said, the group behind this abduction are aware that any harm coming to the people they are holding captive will be met with a swift security response."
The commissioner has previously warned that "specialised security force personnel will use whatever means necessary" including lethal force to secure the release of the hostages.
Second foreign man moved to safety
Another foreigner who had also been working in the same remote area has been moved to safety.
The country's deputy prime minister, John Rosso, said that man was safe and had been cared for by local villagers.
"There is another [expatriate] in the area, in the same area, but has been in the hands of the villagers and that expat is being escorted out of the area."
Mr Rosso said the man was not held hostage at any stage.
"He was in the vicinity at the same time. For his own safety he has been escorted out of the area."
