Several tonnes of fish have died along one of the main rivers in Brazil’s Sao Paulo State after an alleged illegal dumping of industrial waste from a sugar and ethanol plant, environmental authorities and prosecutors said.

A preliminary analysis estimates that between 10 and 20 tonnes of fish died on the Piracicaba River in southeastern Brazil, Sao Paulo’s prosecutors said in a statement.

The initial investigation points to an “irregular discharge of wastewater” from Estiva’s Sao Jose plant in the community of Rio das Pedras and it reached a stream that flows into the Piracicaba River, prosecutors said.