Initial investigation suggests that the American missionary who was killed by indigenous people on an Andaman island last month was on a “planned adventure”, the National Commission for Scheduled Tribes said on Tuesday. The commission’s chairperson, Nand Kumar Sai, said the investigation is still on, PTI reported.

Travel without permission to the North Sentinel island, where John Allen Chau was killed, is prohibited by Indian law. The Sentinelese tribe, whose population was around 40 in 2011, have been known to resist any contact with the outside world.

The panel is attempting to find out who assisted Chau in his journey, Sai said. Seven fishermen who took Chau to the island have been arrested so far.

“Foreign nationals always had an eye on the primitive tribes of these islands and made several attempts in the past to make contact with them,” Sai said. “We need to protect such tribes and their habitat should be completely closed for outsiders.”

The commission’s chief said the incident is not the consequence of the withdrawal of the rule that needed foreigners to obtain a Restricted Area Permit to visit 29 Andaman islands. The requirement of the permit was rescinded in June, but tourists must take permission from the forest department and the administration of the Andaman and Nicobar Islands to visit.

Sai also said that the commission is in the process of taking action against photographs and videos of these tribes posted on social media. However, he added that the panel has suggested to the Centre that it set up universities on islands where the tribes resist contacts with outsiders.

On Monday, Indian Navy Chief Admiral Sunil Lanba had said that there was no lapse in coastal security in the Andaman and Nicobar Islands. Lanba said Chau had permission to visit the island.