Family and friends of an American adventurer killed in a bizarre mission to introduce Christianity to the most isolated Stone Age tribe on Earth say there is a chance he may still be alive.

Police say John Allen Chau, 26, perished on November 16 in a deadly bow and arrow attack by tribesmen desperate to keep him off their remote North Sentinel Island home off the coast of India.

But fellow missionary John Middleton Ramsey says he and Mr Chau’s mother believe there’s a chance he survived the attack, citing a lack of credible witnesses to his death and the failure of authorities to produce a body.

The Sentinelese people have consistently and violently resisted contact with outsiders and only a handful of people have ever set foot on the island, which is protected by a five nautical mile exclusion zone.

Fishermen who illegally ferried Mr Chau to the island say they saw tribesmen drag his body along the beach and bury him in the sand on the morning of November 17 as they watched from a vessel moored several hundred metres from shore.

Officers from India’s police and coast guard are trying to reconstruct Mr Chau’s movements and pinpoint the location of his corpse by observing the tribe’s movements from boats offshore using binoculars.

They have asked for advice from anthropologists and psychologists on how to proceed, ahead of a third visit scheduled this week.

But while police have arrested seven fishermen for their role in helping Mr Chau reach North Sentinel, they have no plans to confront the tribe, let alone lay murder charges.

“They are human treasure, and we respect that,” Dependra Pathak, director general of police in Andaman and Nicobar Islands, told local media.

The community of between 60 and 100 men, women and children have no immunity to disease and exposure to a relatively minor virus like the common cold could wipe them out.

Any mission to retrieve Mr Chau’s body could result in further deaths on both sides and it is likely authorities will leave it behind, just as they did the bodies of two poachers who strayed into Sentinelese waters in 2006 and paid with their lives.

But Mr Chau’s close friend and fellow missionary John Middleton Ramsey said the absence of a body meant there was a chance the young American was still alive.

Mr Ramsey said only one source had been cited in reports describing Mr Chau having been showered with arrows and dragged across the beach by tribesmen.

“I think there’s a possibility he may have survived — I wouldn’t rule it out,” the 22-year-old real estate agent told The Sun online.

“His mother is a Christian too and she has said that in her prayers that she had feelings that John might still be alive

“And there weren’t a whole lot of eyewitnesses and so since his body hasn’t been found we shouldn’t rule it out, even if it is a small chance.”

A family statement posted to Mr Chau’s Instagram account last week referred to “unconfirmed” reports of his death and his mother Linda told The New York Post in an email she believed her son may still be alive.

Mr Ramsey revealed Mr Chau had been planning his trip to North Sentinel Island since high school.

He had hoped to live among the tribe, learn their language, convert them to Christianity and even translate the Bible for them, he said.

“He went on a scouting trip to the area in 2016 —- not to North Sentinel but to the main island to make some local connections,” Mr Ramsey said.

“After returning he told me his plans to go back and it’s not like he was going to start preaching the Bible as soon as he reached the island, he first wanted to get to know the people a little bit.

“He told me he wanted to go alone rather than with the group just to seem as unthreatening as possible and bring some gifts to be endearing.”

Mr Chau first made contact with the Sentinelese on November 15, bringing gifts of fish, scissors, safety pins and a football.

He described the encounter — which did not go well — over several pages of notes passed on for safekeeping just before his death.

“Two armed Sentinelese came rushing out yelling,” he wrote. “They had two arrows each, unstrung, until they got closer. I hollered,” My name is John. I love you and Jesus loves you.”

He offered them some fish but they continued to come at him, infuriated by his unsolicited visit and ham-fisted attempts at interaction.

Close friends are still reeling from missionary John Chau's death (CNN) Close friends are still reeling from missionary John Chau's death (CNN)

One of the tribespeople — reportedly a teenager — fired an arrow at him but it pierced a waterproof Bible he was carrying. He ran to the canoe he had brought ashore and paddled furiously until he reached the safety of the fishermen’s boat several hundred metres away.

It was a warning shot from the tribe but Mr Chau ignored it, paddling back to the island the next morning for round two.

The act tipped the already stressed Sentinelese over the edge and they killed him.

“When I heard about John’s death my immediate feelings where sadness and I naturally shed a few tears but then I was quite shocked by the amount of attention this has received and how polarising it’s been,” Mr Ramsey told The Sun.

“I posted a goodbye picture of him on Instagram and while there’s some people that hail him as a martyr, there’s a ton of hate messages as well. So I must say I was quite surprised by that.

“I support what he was doing. When he spoke with me about his plans before going I encouraged him and I still support what he did.

“You know, it was motivated out of love for these people so I’m behind this. My prayer would be that he’ll be remembered as a martyr.”