In a news conference Wednesday, Amazonas State Security Secretary Carlos Alberto Mansur said the suspect is still under investigation in police custody.
Mansur said the man was arrested after being in possession of “a lot of drugs” and ammunition used for illegal hunting.
Authorities said on Wednesday they were following several lines of investigation, including murder, adding that they still “cannot rule out anything”.
Mansur noted that five other people have also been questioned by police in connection with the disappearance of Phillips and Pereira, who had traveled to the region to conduct research for a conservation book project in the region.
Phillips and Pereira have been missing for more than 72 hours, according to Indigenous Organization Coordination. The organization, known as UNIVAJA, said satellite intelligence showed the couple’s last known location in the community of São Rafael early Sunday morning, where they were expected to meet a local leader who never showed up.
A “dangerous” region
On Wednesday, Federal Police Superintendent Fontes described the area where Phillips and Pereira were missing as “complicated” and “dangerous”.
“In this region, violence is progressing in an increasingly unchecked way in the context of the invasion of indigenous and state-owned lands, repression of press freedom and the work of journalists,” UNIVAJA said in a statement.
In 2018 Phillips reported on the threats of illegal mining and ranching to uncontacted indigenous groups there, with Pereira at the heart of that article.
Survival International, an NGO championing indigenous peoples, said Pereira had previously received “many threats” as a result of his work as an “ally of the indigenous struggle”.
Tara Subramaniam wrote from Washington, DC. Camilo Rocha and Marcia Reverdosa reported from Sao Paulo, Brazil.