Several tons of fish have perished along the Piracicaba River in Brazil's Sao Paulo state due to what authorities suspect is the illegal dumping of industrial waste from a sugar and ethanol plant. Preliminary estimates suggest that between 10 and 20 tons of fish have died, as reported by Sao Paulo's prosecutors. The suspected source of the pollution is an "irregular discharge of wastewater" from the Estiva's Sao Jose plant located in the community of Rio das Pedras, which flowed into a stream that feeds into the Piracicaba River.

Despite multiple requests for comment, Estiva has not responded. Adriano Queiroz, director of licensing at Sao Paulo's environmental agency, highlighted the severe impact on biodiversity, noting that it would take years for the environment to recover due to the significant number and variety of fish killed. The Piracicaba River, which traverses the protected Tanqua area, often referred to as Sao Paulo's mini-Pantanal, covers a basin area of 12,531 square kilometers and is renowned for its abundant wildlife.

On Wednesday, the river was visibly affected, with a thick layer of dead fish floating on its surface, illustrating the extent of the environmental disaster. The incident has not only affected biodiversity but has also raised serious concerns about the well-being of local fishermen and the community. Prosecutors are awaiting a detailed report on water conditions to proceed with actions regarding civil and criminal liability. Meanwhile, police investigations are ongoing to determine if an environmental crime has occurred, with the company facing the possibility of a substantial fine.

The state environmental agency, CETESB, received initial reports of the fish die-off and strong odors on July 7 and subsequently requested the Salto Grande hydroelectric power plant to increase water release to dilute the pollution. By July 9, the amount of dissolved oxygen in the water had increased, improving conditions for fish survival. However, reports of another mass fish die-off emerged in Tanqua, about 60 kilometers from the city of Piracicaba, where the initial news of the dead fish surfaced.

The Piracicaba River is historically significant, running through one of the oldest regions of occupation in Sao Paulo state. It was once used as a navigation route for small steamers and supplied water for sugar cane and coffee farms. This environmental disaster follows a severe drought in the Amazon last year, which also resulted in the death of large quantities of fish.