The wife and mother-in-law of the missing British journalist Dom Phillips have said their hopes of finding him alive had gone, in a heartfelt and heart-breaking message that paid tribute to him and his travelling companion Bruno Pereira. Phillips, a longtime contributor to the Guardian, and Pereira, an experienced Indigenous advocate, went missing on 5 June in a remote part of the western Amazon. Days of searches by army, navy, police and Indigenous residents of the far-flung region have thrown up little trace of the two men and Phillips’ mother-in-law said she had lost all hope of finding them alive. “They are no longer with us,” she wrote on Instagram. “Mother nature has snatched them away with a grateful embrace. The material has been undone and incorporated into the earth they so loved and respected.” “Their souls have joined those of so many others who gave their lives in defence of the rainforest and Indigenous peoples. Today they form part of an immense and pulsating vital energy that emanates from this immense greenery that is the heart of Brazil.” Phillips’ wife posted the statement and said she agreed. The two men went missing at the end of a reporting trip that Phillips undertook as part of a book project on sustainable development in the region. He was travelling with Pereira, a regular guide and friend, to interview Indigenous people in the Vale do Javari, an area almost as big as Ireland and Wales combined. They were reported missing when their boat failed to appear at their scheduled return point in the town of Atalaia do Norte. Authorities have arrested one man, Amarildo da Costa de Oliveira, who was seen threatening Phillips and Pereira the day before their disappearance. Traces of blood found on Da Costa de Oliveira’s boat, and what police called “apparently human organic material” found on the river have been sent for forensic examination along with DNA from Phillips’ and Pereira’s families. Police, however, said they had not tied him directly to the fact. Pereira had been threatened before for his work in the region, where he helped the 26 Indigenous tribes monitor and protect their land. Illegal loggers, miners, hunters and fishers all covet the area’s natural resources and drug traffickers ship their product through the area. The Brazilian government department charged with protecting the Indigenous people and their land has been weakened by the country’s far-right president, Jair Bolsonaro, an unapologetic proponent of Amazonian development. An Indigenous group that works closely with Pereira released a series of documents on Saturday detailing “the modus operandi of criminal gangs” active on their territory. Under Brazilian law, only Indigenous people can hunt and fish on indigenous land but the UNIVAJA group shared details of boats laden with turtles, wild animals and pirarucu – which, at up to three metres, is one of the largest freshwater fish on the planet. Some of the prey is sold openly at markets in Atalaia do Norte, it said, and named local residents it claimed were involved.