Tourists sail in the flooded Amazon rainforest at the Mamiraua Reserve, Brazil's largest protected area, in Amazonas State, on April 25. Photo: AFP

Brazilian authorities on Wednesday arrested a man in connection with the disappearance of a British journalist and a local indigenous expert in the Amazon, police said, as calls mounted for officials to deliver answers on what happened to them.

As the search approached its fifth day, official information was scarce on the investigation into the fate of Dom Phillips, 57, and Bruno Pereira, 41, who disappeared early Sunday in the remote, jungle-covered Javari Valley in Brazil.

Brazilian police and military officers told a news conference they had questioned six people and arrested one. But they said it was unclear whether the suspect was directly linked to the case.

In the meantime, the authorities are pursuing "all lines of investigation," and still hope to find the men alive, said lead investigator Alexandre Fontes.

Investigators said the arrested man was detained during a random stop-and-search operation in the region, when officers found him with drugs and illegally carrying 7.62-millimeter ammunition - a round typically used in assault rifles.

Witnesses reportedly saw the man trailing Phillips and Pereira's boat as the pair made their way back to the small city of Atalaia do Norte after a research trip to an area known as Jaburu lake.

But "we have not established any connection between him and the [disappearance] for now," the Amazonas state security secretary, General Carlos Alberto Mansur, told reporters.

AFP