The same tribe, the Xinane, which had had no contact with the outside world appeared in remarkable footage earlier this year showing them aiming bows and arrows at a plane flying over their jungle home.
But yesterday, after government officials sent to protect them from armed drug traffickers were forced to abandon their post and flee, it was not known where the families were.
It highlights new threats to remote tribes across South America.
Staff at Brazil’s government-run national Indian foundation, Funai, said men from a paramilitary faction from Peru, armed with rifles and machine guns, entered Brazilian territory late last week and surrounded a cut-off jungle post.
A small group of researchers from Funai used the outpost, in Brazil’s Acre state, on its western border with Peru, to study and protect isolated indigenous tribes.
The armed men were most certainly trying to kill Indians in the area to make way for illegal logging, or clear new cocaine trafficking routes through the forest from Peru, said FunaiI.
"This is extremely distressing news,” says Stephen Corry, from Survival International, an indigenous tribes rights group based in Britain. “There is no knowing how many tribal peoples the drugs trade has wiped out in the past, but all possible measures should be taken to stop it happening again."
The Funai staff monitoring the tribe fled and the traffickers ransacked their jungle camp before Brazilian police back-up could reach the area.
Police have since retaken control of the base and arrested one man, named as Joaquim Fadista.
But officials are particularly worried at finding an arrow head in one of the trafficker’s abandoned backpacks.
"Arrows are like the identity card of uncontacted Indians,” said Funai’s Carlos Travassos, who heads its of the isolated Indians division. “We think the Peruvians made the Indians flee…We are more concerned than ever,” he told Christian Science Monitor. This could be one of the biggest blows in decades to the work of protecting isolated Indians."
Funai sent an official to the area but still don’t know the whereabouts of the tribe and it is not known if they are safe. Officials hope they fled the commotion and the Xinane families are safe. It is hoping they fled to seek refuge deeper in the rainforest.
The Xinane were under the spotlight at the start of this year when a BBC nature programme showed footage of the clearly frightened Indians pointing bows and arrows the plane flying overhead.