A man detained due to his suspected involvement in the disappearance of a British journalist and a former government official in the Brazilian Amazon could be held for another 30 days while police investigate the case, a lawyer for a local indigenous organisation said.
Journalist Dom Phillips and Bruno Pereira, a former senior official with federal indigenous agency Funai, have not been seen since last Sunday.
The man who has been detained, a fisherman named Amarildo da Costa, was arrested on Tuesday when he was found in possession of illegal ammunition.
State Judge Jacinta Silva dos Santos said with proceedings under seal, she cannot comment on whether other audiences are planned.
Phillips and Mr Pereira are both experts in the local environment and had been on a reporting trip in the Javari Valley, a remote jungle area that is home to the world's largest number of uncontacted indigenous people.
The area is also frequented by cocaine-smuggling gangs and people engaging in illegal hunting and fishing.

Eliesio Morubo, the lawyer for the Union of Indigenous Peoples of the Javari Valley, said the judge had agreed to keep Mr da Costa jailed for 30 days because the case involved a possible “heinous crime”, such as murder and hiding human remains.
Police have said Mr da Costa was one of the last people to see Phillips and Mr Pereira when they visited the fisherman's riverside community of Sao Gabriel.
Detectives involved in the investigation say they are focusing on poachers and illegal fishermen in the area, who often clashed with Mr Pereira after he organised indigenous patrols of the local reservation.
Mr da Costa's lawyers and family said he fishes legally on the river and denied he had any role in the men's disappearance.

Mr Pareira oversaw the regional indigenous affairs office before going on leave. He reported having received a series of threats from poachers and usually carried a gun.
Phillips has reported from Brazil for more than a decade and was working on a book about the preservation of the Amazon with support from the Alicia Patterson Foundation, which gave him a year-long fellowship for environmental reporting.
The place where the pair went missing is the primary access route to the Vale do Javari, Brazil’s second-largest indigenous territory, which is bigger than Austria or the US state of Maine.
Local people have said it is highly unlikely the men would have become lost in that area.


