Brazilian authorities say possible human remains have been found in a river in the Amazon rainforest where a British journalist and an Indigenous expert went missing on Sunday.
The men disappeared while returning by boat from their reporting trip to the Javari Valley, which sits at the border of Peru and Colombia.
The possible remains were located in the Itaquai River in the upper Amazon basin.
Police say experts will also test "organic material" found on a boat belonging to fisherman Amarildo da Costa and compare it to DNA from the journalist, Dom Phillips, and the Indigenous expert, Bruno Araújo Pereira.
Mr da Costa, who has been charged with illegal possession of restricted ammunition and was one of the last people to see the two men, will be held in custody for 30 days as the investigation continues.
Lawyer Eliesio Morubo, who represents the Union of Indigenous Peoples of the Javari Valley, said Mr da Costa was being detained because the case might involve "heinous" crimes such as murder and hiding bodies.
Police believe the pair's disappearance relates to illegal fishing and poaching activities in Indigenous territories.
'He's innocent', accused man's brother says
Mr de Costa's lawyers and family say he is innocent.
They said he fished legally on the river and alleged police tortured him to get a confession.
Mr da Costa's brother, Osenei da Costa, told Reuters reporters outside the police station where his brother was being held that he had been beaten after being arrested at his home in São Gabriel.
"They put him on a boat under the sun and began to travel to Atalaia do Norte," he said.
"When they reached the Curupira rivulet, they put him on another boat.
"Then they beat him, tortured him, put his head under water, stepped on his leg and pepper-sprayed his face. They also drugged him twice, but I don't know what they used.
Mr de Costa's mother, Maria de Fátima da Costa, said she was at the Atalaia do Norte port when her son arrived with police.
Ms de Costa said he was taken from the boat wearing a hood, unable to walk on his own and soaking wet.
"I told the police he was not a criminal to be treated like that," she said.
She also said the blood police found in her son's boat was likely from a pig he had slaughtered a few days before being arrested.
In a statement, the public security secretariat of Amazonas state — which oversees local police — said it would not comment on the family's accusations of torture by police.
Reuters has contacted Brazil's federal police for comment.
Soldiers deployed after slow response
In Atalaia do Norte, the largest riverside town near where the journalist and Indigenous expert were last seen, the streets have become busy with soldiers in camouflaged trucks and distant sounds of helicopters.
Authorities were facing growing criticism for what was perceived to be their slow response the men's disappearance, with celebrities, politicians and civil society groups calling on the army and navy to boost their efforts.
By Friday, about 150 soldiers had been deployed on riverboats to hunt for the missing men and interview locals.
According to members of an Indigenous group of watchmen who accompanied Mr Pereira and Mr Phillips the day before they disappeared, Mr de Costa and two other men pointed guns at them.
Paulo Maubo, president of the Javari Valley association of Indigenous people, said Mr Phillips had photographed the men while doing this.
But Mr de Costa's family disputed the claims and said an oar was waved at the pair, not a gun.
Mr de Costa's father-in-law, Francisco Conceição de Freitas, told AP he likely felt threatened by the two men, who Mr de Freitas said were armed.
Phillips, 57, has been reporting from Brazil for more than a decade and has been writing a book about the preservation of the Amazon rainforest.
Mr Pereira has long operated in Javari Valley, working with the Brazilian Indigenous affairs agency and also helping local groups defend themselves against illegal fisherman and poachers.
ABC/wires
