(CNN) -- An isolated Indian tribe in Brazil seemingly has vanished like a morning mist in the Amazon jungle.
Concerns are rising that the tribe, filmed this past year for the first time, may have been run off by drug traffickers.
Aid group Survival International first reported this week that suspected traffickers had destroyed a Brazilian guard post built near the tribe's location to protect them from outsiders. The organization said it was feared that a nearby river has become a transit point for cocaine from Peru.
An overflight of huts where the tribe lives showed no one in the area, Bruno Perez, a spokesman for Brazil's National Indian Foundation (FUNAI), told CNN Thursday.
The fact that none of the Indians could be spotted by the air is worrisome, Perez said. However, the huts were still standing and the crops appeared untouched, which indicates that contact was not made, at least not there.
Video of the previously uncontacted tribe, released in February, made headlines around the world, as did 2008 photos of a settlement. In the videos, residents in bright body paint stand near thatch-covered structures.
It's not clear if the images were of the same Amazon tribe.
"We have done overflights before, and they were not scared, and we were even able to take photos of them," Perez said.
It is possible that the Indians fled or were hiding in fear, he said, but added, "We don't know if there was contact."
Authorities recovered a backpack, believed to belong to a drug trafficker, that had an arrow inside of it.
A clue, but "that doesn't mean there was contact," Perez said.
More than 100 uncontacted tribes remain worldwide, and about half live in the remote reaches of the Amazonian rainforest in Peru or Brazil, says Survival International, which advocates for tribal peoples. It refers to such tribes as "peoples who have no peaceful contact with anyone in the mainstream or dominant society."
Brazil and Survival International have warned of the dangers posed by logging and disease.
Loggers in Peru are pushing isolated Indians from Peru into Brazil, where, according to Survival International, "the two groups are likely to come into conflict."
Brazilian authorities said they know that the armed men seen in the area -- about 40 of them -- crossed the border from Peru, but they don't know the nationality of the suspected traffickers or with what criminal organization they might work.
The incursion was first reported by Indians from the Ashaninka people, who at the end of July reported to Funai that a group of armed men from Peru ransacked their village. This village was about five days by boat away from the area where a number of isolated and uncontacted tribes reside, Funai said.
As a result, Brazilian authorities dispatched a group of federal police to the region.
Maj. Luis Baca of the National Police of Peru told CNN that they have an outpost on the Peruvian side not far from where the armed men were spotted, but said that he had not received any recent reports of traffickers in that area.
Perez, of Funai, agreed that drug trafficking in the area was new.
"In this region, drug trafficking is an isolated problem," he said.
It was the first time that traffickers were suspected of crossing from Peru in the area near the Indian tribe.