(BBC) The wife of a British journalist who disappeared in the Brazilian Amazon has urged the country's authorities to do more to find "the love of my life".
Dom Phillips, 57, went missing in a remote part of the Amazon on Sunday along with Brazilian indigenous expert Bruno Araújo Pereira, 41.
In an tearful video, Mr Phillips's wife Alessandra Sampaio said she still had "some small hope" of finding them.
Mr Pereira's family have also asked the authorities to speed up the search.
On Tuesday, Brazil's President Jair Bolsonaro appeared to blame the missing men for their disappearance.
"Two people in a boat in a region like that, completely wild - it's an unadvisable adventure. Anything can happen," he said.
"Maybe there was an accident, maybe they were executed," he said. Brazilian police have opened a criminal investigation following news that Mr Pereira had been threatened.
Mr Pereira, an expert on isolated tribes in the Amazon who has worked for the government's indigenous affairs agency Funai, had clashed with some in riverside communities over illegal fishing.
Dom Phillips, a veteran journalist, was travelling with Mr Pereira by boat through the Javari Valley near Brazil's border with Peru as part of his research for a book on conservation efforts in the Amazon.
The huge region is home to around 6,300 indigenous people from more than 20 groups and is under threat from illegal loggers, miners and hunters.
Indigenous rights groups that Mr Pereira worked with raised the alarm when the two failed to arrive as planned in the municipality of Atalaia do Norte on Sunday.
The groups said that Mr Pereira had received death threats in the week before his disappearance over his fight against illegal fishing.
Reuters news agency reported that the police had interviewed several local fishermen - including one man who is being treated as a potential suspect - who are believed to be among the last people to have seen the journalist and indigenous expert in the Javari Valley.
Denis Paiva, the mayor of Atalaia do Norte, told Reuters that the suspect had been taken to a local police station in handcuffs.
Police are also trying to locate the fisherman suspected of writing a threatening letter to Mr Pereira just last week.
The rights group which first sounded the alarm about the disappearance said that the security forces had failed to follow up on key leads.
Eliesio Maruba of the Univaja rights group said that neither the police nor the navy had turned up to a scheduled meeting at which Univaja wanted to inform them about those it suspects of being behind the threats and their whereabouts. The response by the Brazilian authorities has been widely criticised as slow and inadequate.
At first, only about a dozen people were sent to search the vast rainforest area crisscrossed by rivers. A helicopter was only sent on Tuesday and the number of soldiers deployed has been upped to 150.
But the sluggishness of the search has caused further anguish for the men's families.
Mr Pereira's wife has also released a video message urging quicker action and saying that she hoped the men's disappearance was down to their boat breaking down.
However many fear the pair may have been targeted.
As well as rising tension over illegal fishing, the area has seen incursions by illegal gold miners, loggers and drug traffickers who smuggle cocaine from neighbouring Peru.
Mr Phillips has documented many of these threats in his articles for the Guardian newspaper in the UK as well as other publications such as the Financial Times and the Washington Post.
Colleagues of the two have stressed that the men have deep knowledge of the region and carefully planned their trip.