Dom Philips, who works for The Guardian, and Bruno Araujo Pereira, an expert on local communities, disappeared in the area.
Officials said that they had not heard from the duo since the early hours of 5 June, who were expected to return from the Vale do Javari region where they were by boat.
On the other hand, it was stated that Pereira had previously been threatened by poachers in the Vale do Javari region, where he was conducting research.
With many villages, Vale Do Javari is the second largest local area in Brazil. Government officials frequently interfere with fishermen and poachers in this area.
While an investigation into the incident was launched by the Brazilian Federal Prosecutor yesterday, the search continues, for which the navy gave reinforcements.