But before they can even attempt to recover the body of 26-year-old John Allen Chau, authorities have to learn from antropologists "the nuances of the group's conduct and behaviour, particularly in this kind of violent behaviour," said Dependra Pathak, the director-general of police of the Andaman and Nicobar Islands, where North Sentinel Island is located.

During their visit to the island's surroundings on Friday, investigators spotted four or five North Sentinel islanders moving in the area from a distance of about 500 metres from a boat and studied their behaviour for several hours, said Pathak.

"We have more or less identified the site and the area in general," Pathak said by phone on Saturday.

Indian authorities have been struggling to figure out how to get the remains of Chau, who was killed by North Sentinel islanders who apparently shot him with arrows and then buried his body on the beach.

Friday's visit was the second boat expedition of the week by a team of police and officials from the forest department, tribal welfare department and coast guard, Pathak said.

The officials took two of the seven people arrested for helping Chau get close to the island in an effort to determine his route and the circumstances of his death. The fishermen who had taken Chau to the shore saw the tribespeople dragging and burying his body on the morning of November 17.

Officials typically don't travel to the North Sentinel area, where people live as their ancestors did thousands of years ago. The only contacts, occasional "gift giving" visits in which bananas and coconuts were passed by small teams of officials and scholars who remained in the surf, were years ago.

Indian ships monitor the waters around the island, trying to ensure outsiders do not go near the Sentinelese, who have repeatedly made clear they want to be left alone.

Chau went to "share the love of Jesus," said Mary Ho, international executive leader of All Nations. All Nations, a Kansas City, Missouri-based organisation, helped train Chau, discussed the risks with him and sent him on the mission, to support him in his "life's calling".

"He wanted to have a long-term relationship, and if possible, to be accepted by them and live amongst them," she said.

In an Instagram post, his family said it was mourning him as a "beloved son, brother, uncle and best friend to us". The family also said it forgave his killers.

Australian Associated Press