The Andaman and Nicobar Police arrested seven fishermen in connection with the murder of an American tourist, NDTV reported on Wednesday.

The seven fishermen took tourist John Allen Chau to North Sentinel Island, where people of the indigenous Sentinelese tribe live. The Sentinelese, whose population was around 40 in 2011, have been known to resist any contact with the outside world.

Chau was attacked with bows and arrows after he landed on the island on November 16, the fishermen told the police. They claimed to have seen the island’s indigenous people drag him to the beach before they lost sight of him.

The police are using helicopters to search for the body but have not been able to land because of the protected tribe’s alleged hostility. Police officer Deepak Yadav said an investigation into the matter was initiated after the US consulate in Chennai contacted the department, Reuters reported.

Meanwhile, Survival International, a movement for Adivasi rights, issued a statement accusing the Indian government of failing to protect the Sentinelese people and their island for the safety of both the tribe and outsiders. “A few months ago the authorities lifted one of the restrictions that had been protecting the Sentinelese tribe’s island from foreign tourists, which sent exactly the wrong message, and may have contributed to this terrible event,” the organisation added.

Stephen Corry, the organisation’s director, expressed hope that the incident would be an eye-opener for authorities. “It’s not impossible that the Sentinelese have just been infected by deadly pathogens to which they have no immunity, with the potential to wipe out the entire tribe,” Corry said. “The Sentinelese have shown again and again that they want to be left alone. Uncontacted tribes must have their lands properly protected.”

The US consulate told Reuters that it was in contact with Chau’s mother. “We are aware of reports concerning a US citizen in the Andaman and Nicobar Islands,” a consulate spokeswoman said in an email. “When a US citizen is missing, we work closely with local authorities as they carry out their search efforts.”

In 2017, the Andaman and Nicobar administration had clarified that the uploading of pictures or videos of tribes on the islands was punishable with imprisonment up to three years.

In 2006, two fishermen, whose boat had purportedly strayed into Sentinelese territory, were killed, Reuters reported.