Half of the territory reserved for indigenous communities along River Guama in the state of Para, northern Brazil, has been seized by drug traffickers, loggers, and farmers, according to a report in O Globo.
According to the newspaper, drug traffickers have been growing marijuana in the reserve, which covers 279,000 hectares.
They have been enforcing control by threatening local indigenous people, and have driven up rates of drug addiction in the area.
Elsewhere in Para state, in Brazil's Amazon, at least six killings in recent months have been linked to land conflict, with illegal loggers clashing with local people and environmental activisits.