Indigenous rights advocates called on Brazil on Thursday to officially recognize an uncontacted tribe in the Amazon rain forest, and to give its members their constitutional rights to protected territory, as the group is increasingly threatened by illegal logging. But with the tiny tribe’s very existence in dispute, constitutional protection has proven hard to deliver.

Several uncontacted tribes reside deep in remote areas of the Amazon, and remain isolated largely because of long-running threats of violent interactions with outsiders — beginning with European colonizers and continuing until today, with companies looking to exploit resources such as lumber.

The Brazilian government’s National Indian Foundation (FUNAI) estimates there are about 77 uncontacted tribes currently living in the Amazon jungle. One such group, the Kawahiva, lives in Brazil's Mata Grosso state and consists of only about 50 people who have in recent years been increasingly threatened by logging activity, FUNAI says.

"For decades, powerful and corrupt politicians and ranchers have denied the existence of uncontacted tribes in the name of profit," Stephen Corry, director of London-based indigenous rights organization Survival International, said in a news release.

Despite video footage of the Kawahiva taken in 2011 by a Brazilian government team during a chance encounter, many in the resource extraction industries have consistently denied their existence.

"The longer Brazil allows people like Riva to plunder the land and resources of the Kawahiva, the greater the risk this tiny tribe will be wiped out forever,” Corry said. “Brazil can easily stop this happening simply by protecting their land."

Little is known about the Kawahiva. Evidence suggests that they recently left a more sedentary lifestyle in which they cultivated corn and other crops, and appeared to be on the run, Brazilian news agency El Pais reported in October.

FUNAI said it found hastily abandoned settlements in the forest near the Pardo River in Mato Grosso late last year. The apparently fleeing tribe had left behind bows and arrows, as well as food including birds, fish, fruits, nuts and berries. Palm-branch fences were built around the camp, FUNAI reported.

FUNAI hopes to use the video footage of some members of the Kawahiva as evidence of their existence in the face of denials from logging companies, and to pressure the public and government to ensure the protection of the tribe’s territory, El Pais reported.

Brazil’s constitution says the indigenous peoples’ territories must be protected — but the Kawahiva's disputed existence has prevented taking steps to do so.

Gaining government protection of the Kawahiva's territory is more important than ever, Survival International said, warning that entire tribes can be wiped out by contact — sometimes violent — with outsiders. Brazil has a policy of avoiding contact with members of uncontacted tribes, for fear of passing on germs for which they have no immunity.

But illegal logging poses an even more immediate threat that disease to the Kawahiva living along the Pardo River, El Pais said.

Illegal logging accounts for some 90 percent of the income of the Colniza municipality, one of Brazil’s most violent frontier towns in one of Mato Grosso’s most deforested areas, El Pais added.

"They don't care that their rapaciousness is leading to the annihilation of entire peoples," Survival International's Corry said in the release.