Three other people have been arrested in connection with the killings of British journalist Dom Phillips and Brazilian indigenous expert Bruno Pereira.
Police in Brazil believe the suspects were involved in hiding their bodies in the Amazon rainforest after the murder.
Although they gave few details, a statement from the force said they were relatives of fisherman Amarildo da Costa Oliveira.
Known as “Pelado”, he is one of three men previously charged with the murder of the two men.
Veteran reporter Mr Phillips, who was chronicling worsening deforestation in the Amazon, and activist Mr Pereira disappeared in June in a remote part of the rainforest.
Her remains were found after Oliveira “told officers he used a firearm to kill the two victims.”
He allegedly took them to the spot where they were buried, near the entrance to the Javari Valley indigenous territory, which borders Peru and Colombia.
So far, a total of seven people have been arrested for their alleged involvement in the killings or attempted cover-up.
Last month, three men were charged in their murders.
Prosecutors say the suspects were fishing illegally in the Javari Valley when they encountered Mr Phillips and Mr Pereira.
It is alleged that they gunned down the two men because they asked to photograph the suspects.
Police also identified a man arrested in early July for allegedly having false documents on him as Ruben Dario da Silva Villar, known as the “Colombian”.
The statement described him as “the leader and financier of an armed criminal organization dedicated to illegal fishing in the Vale do Javari region and responsible for marketing a large quantity of fish that was exported to neighboring countries”.
In addition to the three people arrested for alleged involvement in hiding the bodies of Mr Phillips and Mr Pereira, two other people have been arrested in the investigation into illegal fishing, police said.
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https://metro.co.uk/2022/08/07/brazil-three-more-arrests-over-british-journalist-killed-in-amazon-17142149/ Brazil: Three more arrests over a British journalist killed at Amazon