SAO PAULO (AP) — Brazil's Indigenous affairs agency on Tuesday launched an expedition that activists fear could endanger a large protected area for isolated people in the Amazon region that has been targeted for development by ranchers, miners and other land-hungry interests.

The mission went forward even though prosecutors in the city of Altamira this week warned the National Indian Foundation that officials could face legal sanctions unless they called off the expedition, which potentially could lead to decertification or reduction of the Ituna-Itata reserve.

It's been at least 35 years — when military rule ended — since any designated Indigenous territory in Brazil has been eliminated or reduced in size.

Those territories have long irked President Jair Bolsonaro, who complains that too much land has been allotted to small Indigenous populations, impeding economic development. He has pledged not to allocate any new lands for them, saying the designated areas have them living “like prehistoric beings.”

So far he hasn't taken any away. But Ituna-Itatu may be in danger, potentially creating a precedent for reducing other areas reserved for isolated Indigenous people.

Documents seen by The Associated Press show that leaders of the agency known as FUNAI in March drafted a proposed decree — not yet announced or enacted — that would roughly halve the size of the 140,000-hectare (540-square-mile) territory.

It is one of seven “temporary” territories created over the past quarter century in Brazil to protect uncontacted or isolated groups whose existence is not yet fully established — giving those living in hiding room to hunt, gather and cultivate without risk of contact with outsiders who could bring diseases to which they are vulnerable. Officials say there are believed to be 86 such groups across Brazil.

Twenty-eight known groups living in voluntary isolation are also protected in other, permanent territories.

Following a phone call and emails from the AP on Friday and Tuesday, FUNAI didn't answer questions about the expedition to the territory or its proposed reduction.

The agency’s president, federal police officer Marcelo Xavier, said at a public hearing last year that he won’t consider “fraudulent anthropologic reports” that believes to be contaminated by leftist ideology.

Internal FUNAI maps that appear to show the proposed cut to Ituna-Itatu “were drawn before any expeditions took place” to determine where isolated people are living and what should be protected, said Leonardo Lenin, secretary-general of the nonprofit Observatory for the Human Rights of Uncontacted and Recently Contacted Tribes, known by its local initials as OPI.

But he said that according to the maps, "those very lands they might cut are currently invaded.”

Satellite surveys have shown extensive recent deforestation in a region that was almost untouched a decade ago, and local agricultural and mining interests led by Sen. Zequinha Marinho— a close ally of Bolsonaro — have pushed for it to be open, arguing there's no evidence of Indigenous people there. Construction of the huge Belo Monte dam nearby has stimulated some of that activity.

Deforestation in Brazil has surged to a 12-year high, according to data the government's space research institute released Monday. The world's largest tropical rainforest lost 11,088 square kilometers (4,280 square miles) from August 2019 to July 2020, up 9.5% from the prior 12-month period.

Greenpeace Brazil reported in May that private individuals have filed claims to 94% of the territory in Ituna-Itatu — many of them for tracts large enough to hold a big cattle ranch.

The temporary reserves must be recertified each three years with survey studies showing strong evidence of the continuing existence of isolated peoples, who can be hard to track in the jungle region precisely because they try to avoid contact. Previous expeditions have found strong evidence of isolated groups — structures, baskets, camps — though no direct sightings.

Without such evidence, the territory could be decertified, potentially open to development. And changes to such allotments can be made by the executive branch with no action by Congress, unlike permanent ones.

FUNAI workers with knowledge of the operation said the agency sent a survey expedition to Ituna-Itata on Tuesday, alarming OPI, which says current conditions almost guarantee it will fail. The planned mission prompted it to seek action by prosecutors. The FUNAI workers spoke to the AP on condition of anonymity for fear of retaliation.

OPI's Lenin said that a reliable ground-based survey is impossible at the moment. That's in part because the COVID-19 pandemic makes accidental contact hazardous to any isolated tribes especially vulnerable to infection: “We fear this expedition could become a super-spreader in a territory of isolated Indigenous,” he said.

But the main concern “is the security of the team that will go there,” he said. “Last year, agents of (Brazil’s environmental regulator) IBAMA went to Ituna-Itata to do their work and those invaders kicked them out.”

“There must be expeditions on Indigenous land," Lenin said, "but not in this context. And to do expeditions you have to remove invaders from Indigenous land first.”

FUNAI apparently plans to depend largely on an aerial survey using infrared detectors, though the military, which would host that effort, has said in documents that such methods are unreliable.

Prosecutors acting on the OPI request issued a warning to FUNAI on Sunday, giving the agency until Tuesday morning to respond to the allegations.

“The information we have is that they will ignore the warning of the prosecutors and go ahead with the expedition anyway," Lenin said.