Brazilian police investigating the disappearance of a British journalist and an indigenous expert in the Amazon rainforest are focusing on people involved in illegal fishing and poaching in indigenous lands, three officers told Reuters.

Two of the officers are Amazonas state police detectives directly involved in the case, while the other is a senior Brazilian federal police officer tracking it closely. They requested anonymity to discuss an ongoing investigation.

“The principal criminal hypothesis at this point is that the people involved, and their motive, was related to illegal fishing and poaching activities in indigenous territories,” said the federal police officer.

Witnesses said they last saw Dom Phillips, a freelance journalist who has written for the Guardian and the Washington Post, on Sunday. Phillips was traveling deep in a lawless part of the Amazon rainforest with Bruno Pereira, a former official with federal indigenous agency Funai.

Phillips and Pereira were on a reporting trip in the Javari Valley, a remote jungle area near the Peruvian and Colombian border that is home to the world’s largest number of uncontacted indigenous people. The wild, unruly region has lured cocaine smugglers, as well as illegal hunters and fishermen.

Fishermen and poachers travel deep into the Javari Valley, next to the border with Peru, to find protected species like the pirarucu fish, which are sold in regional markets in nearby cities such as Tabatinga. In 2019, Maxciel Pereira, who worked with Funai to shut down illegal fishing in the Javari Valley, was shot dead in Tabatinga.