An Australian archaeologist and two Papua New Guinea researchers held for a week by 20 armed men in a remote part of the Pacific Island nation were released on Sunday, while their captors remain at large, a local official told Reuters.

Professor Bryce Barker and doctoral student Teppsy Beni from the University of Southern Queensland, and Papua New Guinea National Museum researcher Jemina Haro were released after a ransom payment, said Alphonse Seiyaka, an official with the government of Mount Bosavi, where the three were held in rugged terrain.

“They didn’t catch the criminals,” Seiyaka said. As soon as soldiers exchanged money for the Australian and the two Papua New Guinea women, he said, the captors “ran away into the bush”.

Seiyaka declined to specify the ransom amount but said it was less than the 3.5 million kina ($960,000) initially demanded.

Australian Foreign Minister Penny Wong thanked the Papua New Guinea government for “securing a safe and peaceful resolution”.

Papua New Guinea Prime Minister James Marape said this was the first such incident in his country and “it must not be repeated”.

“The police and the army have surrounded the area and will be operating there until you surrender,” he warned the armed men in a statement.

Barker’s team was investigating whether Papua New Guinea provided the bridge for the first human migration to Australia tens of thousands of years ago. The remote village of Fogomaiyu, in the Mount Bosavi region in Hela province, is part of the collapsed cone of an extinct volcano.

The group, seized on Feb 19 in Fogomaiyu village, was taken 10 kilometers into the bush.

The University of Southern Queensland was “relieved to hear that our much-loved colleague” had been released, said vice-chancellor Geraldine Mackenzie.

“Our deepest thanks go to the governments of Papua New Guinea, Australia and New Zealand, and the many people who worked tirelessly during this extremely difficult and sensitive time to secure their release,” she said in a statement.

Cathy Alex, captured with the others and released on Wednesday, had taken leave from her job as a project coordinator for the PNG Women Leaders Network (WLN) in Port Moresby to join the field trip studying the Great Papuan Plateau.

WLN president Ruth Kissam said Alex is a regular visitor to the Mount Bosavi area.

“This is someone the community loves. She has a tribe that has adopted her. The people involved in this situation are criminal elements who are not from the area,” she said.