The family and rights groups of a British journalist and a Brazilian Indigenous specialist who went missing deep in the Amazon after receiving threats urged Tuesday authorities to expedite the search.

Dom Phillips, 57, a veteran freelance writer, and Bruno Pereira, 41, a known Indigenous specialist, went missing early Sunday while sailing in Brazil's Javari Valley, bordering Peru, when Phillips was investigating a book.

As the 48-hour mark approached, questions arose over whether they were victims of an accident or foul play.

Authorities had no information on their whereabouts as of Tuesday night, but Amazonas state civil police stated they were interviewing a "suspect" and that four other persons had testified as "witnesses", though no arrests had been made.

According to local Indigenous activists, the couple received threats last week as a result of their work in the isolated region, which has experienced an increase in illicit logging, gold mining, poaching, and drug trafficking.

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"I want to make an appeal to the government to intensify the search," Phillips's Brazilian wife, Alessandra Sampaio, expressed in a video statement.

"We still have some small hope of finding them. Even if I don't find the love of my life alive, please find them," she said. 

Authorities were accused of not responding quickly enough, while the Brazilian government voiced "grave concern", and police stated they were taking "all possible measures to find (the men) as quickly as possible."

According to the Ministry of Defense, the army has dispatched 150 soldiers who are "specialists in jungle environment operations, who know the terrain where the searches are being carried out," since Monday.

However, three Indigenous rights groups in the region previously disclosed that just six state police personnel were actively engaged in the operation, and they encouraged the government to deploy helicopters and a task force.

"The Brazilian government was very slow to act, in a situation where acting quickly is absolutely essential," the World Wildlife Fund (WWF) Brazil office stated.

According to Brazil's federal police, a second helicopter was deployed to help the search efforts.

Bolsonaro's comment under fire

President Jair Bolsonaro has come under fire for appearing to blame the missing men, both of whom have vast expertise in the Amazon jungle region.

Bolsonaro stated that "two people in a boat in a region like that, completely wild -- it's an unadvisable adventure. Anything can happen."

"Maybe there was an accident, maybe they were executed."

Bolsonaro has faced criticism for fueling pro-mining policies in Indigenous lands in the Amazon and Pereira, an expert currently on leave from Brazil's Indigenous affairs agency FUNAI, has campaigned against such policies, often being threatened as a result.

Painful waiting

According to Pereira's family statement, if either of the men is injured, time is of essence to the search and rescue operation.

They added that they were in anguish, while Philip's sister Sian posted a video statement on the edge of tears.

Sian stated that "every minute counts," urging the Brazilian authorities to act quickly.

In a letter published in the Brazilian daily O Globo, a group of approximately 40 reporters and friends of Phillips urged Brazilian authorities to widen the search.

In addition, 11 news organizations asked for an emergency meeting with the justice minister and other high-level authorities to obtain an update on the hunt.

Phillips, who lives in Salvador, previously followed Pereira to the Javari Valley in 2018 for a piece in Britain's Guardian newspaper, where he was a frequent writer.

Around 6,300 Indigenous people from 26 tribes live on the 85,000-square-kilometer (33,000-square-mile) reservation, which has little contact with the outside world.

FUNAI's outpost there, which was established to safeguard Indigenous populations, has been attacked multiple times in recent years, including the death of an officer in 2019.

According to Fiona Watson, research director at Indigenous rights group Survival International, the region has experienced an increase in illicit mining, logging, and poaching in recent years, and its remoteness makes it a sanctuary for drug traffickers.

She told AFP that "you're talking about dense tropical forest," describing the locating of Bruno and Dom as "immensely challenging".

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