A Brazilian environmentalist group says that toxic waste from a mine dam collapse wiped out life in more than half the Paraopeba River that flows past the city where the disaster occurred.

SOS Mata Atlantica said environmentalists traveled 305 of the river’s 510 kilometers (190 of 315 miles) and found that aquatic life was unsustainable.

The report was released on Wednesday.

The report said heavy metals, such as manganese, copper and chromium, were detected at levels higher than recommended, and it added that mud destroyed 112 hectares (277 acres) of native forests

The dam holding back iron ore tailings at a mine owned by Vale SA burst Jan. 25 in the town of Brumadinho, killing at least 186 people.