The American national killed by the Sentinelese tribesmen in the Andaman and Nicobar Islands last month was pursuing a "planned adventure", the National Commission for Scheduled Tribes (NCST) has said.
An earlier report had indicated that he might have ventured into the prohibited island to preach Christianity.
"Preliminary investigations suggest that it was a planned adventure trip by the American national, John Allen Chau. The investigation is still on," he said.
Seven people were arrested in the case so far, Sai said, adding that efforts were on to identify the others who had assisted Chau in his journey.
"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. We need to protect such tribes and their habitat should be completely closed for outsiders," Sai said.
The NCST chairperson said the incident had no link with the withdrawal of the Restricted Area Permit (RAP).
Even though the RAP has been withdrawn, a tourist is required to take permission from the forest department and the administration of the Andamans as the area is protected.
The administration and the inhabitants of these islands should be more vigilant in view of the incident involving Chau, the NCST chairperson said.
The commission was taking action against those who had posted photos and videos of these tribes on the social media, he added.
The tribal communities of these islands were divided into two categories -- one that was now part of the mainstream and the other that resisted contact with outsiders -- and there was a need to preserve those in the second category, Sai said.
The NCST had suggested setting up of a university on these islands for the development and education of the tribal communities there, he added.
Hours before he was killed, Chau had survived an arrow attack from a short-statured tribesman as it had hit the Bible he was carrying, the diary notings of the American national revealed.
(With inputs from agencies.)