A recently discovered tribe of indigenous Brazilians was reportedly attacked by a Peruvian drug gang. Officials in Brazil say that a group of armed men stormed a jungle outpost than ransacked tribal land in July, scattering and possibly killing the native residents.

Researchers and members of FUNAI, Brazil's department for indigenous affairs, returned to the land and sent back reports Monday, and have so far been unable to locate the tribe. They now fear that the group has been wiped out permanently.

"We decided to come back here because we believed that these guys may be massacring the isolated [tribe]," Carlos Travassos, the head of Brazil's department for isolated indigenous peoples, told the Brazilian news Web site IG.

“We think the Peruvians made the Indians flee… We are more worried than ever," he said.

"The situation could be one of the greatest blows we have seen to the work to protect isolated Indians in decades. A catastrophe … genocide!"

Jungle guards reportedly found a backpack punctured with broken arrows on the tribe's now-empty land. The bag is assumed to have belonged to one of the armed men who stormed the area with rifles and machine guns. Police have detained a Portuguese man with a criminal record in connection with the event.

"Arrows are like the identity card of uncontacted Indians. We think the Peruvians made the Indians flee. Now we have good proof," Travassos added.

According to some accounts coming from Brazil, the Peruvian gang may still be present in the area, protecting the land with machine guns. It is assumed that the gang wants to use the territory to establish a trafficking route to Acre, Brazil, or to harvest the coca plant, used to make cocaine.

"We are extremely worried about this situation," Fiona Watson, Brazil campaigner for Survival International told The Guardian. "It really highlights how out of control things are on the Peru side, and the urgent need for constant, long-term protection for the uncontacted tribes on both sides of the border."

Authorities also found a bag of cocaine near the grass huts where the tribe used to live.

Brazil first released photos of the tribe in February. They were discovered during a flyby in 2008. Brazil has an outstanding policy not to contact isolated tribes, choosing instead to monitor them sporadically. Nonetheless, the tribes often meet, and are sometimes killed by, land developers trying to seize the jungle plots.