During an aerial inspection of the area, Brazilian government officials spotted a village and various hunting camps. They also found felled mahogany trees and drums of chainsaw oil floating down the Envira River.
The Brazilian government estimates that there are already three different uncontacted groups living in this region. Officials fear that as more uncontacted Indians seek refuge from Peru, fatal conflicts may break out between them.
José Carlos dos Reis Meirelles Júnior, head of a Brazilian government post on the Envira River, said, "The most important thing is not to know who they are or to which group they belong, but to protect them, guarantee their territory and let them live how they wish."
Commenting on the story, Stephen Corry, director of Survival International, said, "Unless the Peruvian government acts now to stop logging in the lands of these uncontacted Indians, they may well be consigned to history as the first peoples to disappear this century."
Last month, it was reported that two children from Brazil's Guarani Kaiowá tribe had died of starvation, and several dozen were being treated in hospital for severe malnutrition.
Within days of the children's deaths, Valdinez Souza, a Guarani health worker and father of two children, hanged himself. He left a note by his body saying he had killed himself because children in his community are suffering from acute hunger.
Despite this alarming situation, the Mato Grosso do Sul state government has cut food aid to the Guarani.
Brazil's health foundation, FUNASA, says it will distribute food baskets to needy families, but many fear this will only be a temporary measure.