The Federal Police have opened an investigation into the possible contamination of the Waimiri Atroari Indigenous Territory, in the state of Amazonas, by Mineração Taboca, the country's largest producer of refined tin. The investigation was launched at the request of the Federal Public Prosecutor's Office in Amazonas, which has been monitoring the case since 2021, when heavy rainfall caused mining waste to overflow into the rivers that run through the Indigenous territory. In April 2026, the Waimiri Atroari expressed concern over an alleged new wave of pollution. Large patches of mud with a “strong odour” and a “murky appearance” were reportedly found in a stream that flows through the mining area and empties into the territory's main river. In the following weeks, river dolphins, turtles and a freshwater stingray were found dead.