Dom Phillips disappeared with Bruno Araujo Pereira, a local indigenous expert in Brazil whose mission was to preserve uncontacted tribes. A state official stated that he could not rule out the possibility that their disappearance was associated with criminal gangs operating in the lawless Javari Valley.

The disappearance of a British journalist in the Amazon jungle has prompted the Brazilian police to launch a criminal inquiry.

Dom Phillips and Bruno Araujo Pereira, a former government official whose duty was to safeguard uncontacted tribes in Brazil, went missing on Sunday.

At least four witnesses believed to be among the last to have seen Mr. Phillips, a freelance journalist who has written for The Guardian, The Washington Post, and The New York Times, have been interviewed by police.

Guilherme Torres, the commander of the interior division of the state’s civil police in Amazonas, told Reuters that Mr. Pereira had lately received a threatening letter from a local fisherman, whom police were attempting to locate.

According to him, his colleagues questioned two fishermen as witnesses on Monday, and two more on Tuesday.

The first two witnesses had supplied no useful information, and Mr. Torres did not have any information regarding the second two interviews.

“We are operating on the assumption that a crime may have occurred, but there is another, much more likely scenario that they are missing,” he said.

“Now, finding them alive is our first concern, particularly in these initial hours. In parallel, a criminal investigation has been launched to determine whether a crime has been committed.”

The Brazilian navy and army have despatched search teams in boats and helicopters to locate the two individuals, with the assistance of federal and state police officers.

57-year-old Mr. Phillips and his guide went missing during a reporting expedition in the Javari Valley.

The huge region on the border with Peru is home to the greatest number of uncontacted indigenous people in the world and is threatened by illegal miners, loggers, hunters, and coca-growing gangs that produce cocaine’s raw ingredient.

Mr. Torres stated that he could not rule out the possibility that their disappearance was connected to the gangs operating in the chaotic area.

Saturday, armed individuals threatened an indigenous patrol, according to the Union of Indigenous Peoples of the Javari Valley, which made the initial announcement of their disappearance.

The confrontation was reportedly caught on a mobile phone.

The abduction of the two men, who both had years of experience working in the complicated and unforgiving Amazon rainforest, sparked worldwide concern among human rights organizations, environmentalists, politicians, and press freedom supporters.

In an emotional televised interview, Alessandra Sampaio, the wife of Mr. Phillips, encouraged authorities to increase their search efforts “because we still have some hope of locating them.”

She said, “Even if I don’t find the love of my life alive, please locate them.”

“I am quite nervous. I’m quite concerned. It is your greatest dread “Ms. Phillips stated.

“We need to throw everything at this problem. We want British officials to exert pressure on the Brazilian government to take action.”

Mr. Pereira’s family issued a statement requesting a thorough search, adding, “we are also extremely hopeful that there was an accident with the boat and that they are awaiting assistance.”

President Jair Bolsonaro stated in a televised interview on Tuesday that the two men were “engaged in a dangerous adventure.”

“It may have been an accident or they could have been executed; everything is possible,” he remarked. “I hope and we pray that they are found quickly.”

Mr. Phillips had confronted the Brazilian president with difficult questions at press conferences over policies that have hampered the country’s environmental law enforcement.

Since Mr. Bolsonaro’s ascension to office, indigenous patrols have often complained about weakened environmental law enforcement and demanded fewer restrictions on tribal properties in the Javari Valley.

Additionally, they frequently engage with illegal miners and hunters in the region.

Mr. Phillips had been conducting research for a book on the Amazon and its environmentalists.