The Piracicaba River crosses a protected area named Tanqua, that has been dubbed Sao Paulo’s mini-Pantanal, after the tropical wetlands famous for abundant wildlife and dazzling natural scenes. Its basin covers an area of 4,838 square miles.
On Wednesday, a carpet of floating fish corpses covered the waterway, littering stretches of the river.
“This sad environmental disaster has moved everyone because of the seriousness and extent of the impacts,” prosecutors said, adding that the situation of the fishermen and the local community is also “very worrying.”
Prosecutors have requested a full report into conditions of the water and are waiting for further technical information before taking the next steps regarding civil and criminal liability.
Police are investigating to determine if an environmental crime was committed, Sao Paulo’s secretary for public security said in a statement.
The company risks a hefty fine.
Sao Paulo’s state environmental agency, known in Portuguese as CETESB, first received reports of the mass die-off and strong odor emanating from the river on July 7.
That same day, the agency asked the Salto Grande hydroelectric power plant to increase the amount of water released to dilute the pollution.
By July 9, data showed an increase in the amount of dissolved oxygen, favoring conditions for survival of the fish, CETESB said.
But reports emerged of another mass die-off in Tanqua, about 37 miles from the city of Piracicaba where news of dead fish first emerged.
The Piracicaba River runs through one of the oldest regions of occupation of Sao Paulo state and was used as a navigation route for small steamers and supplied water for sugar cane and coffee farms, according to the country’s national statistics agency.
A severe drought in the Amazon also killed huge quantities of fish last year.
