No toxic substances proven to cause fish death in Odra says minister

No toxic substances have been found in water samples taken from the River Odra, where masses of dead fish have been found, Poland's climate and environment minister has said. More than ten tonnes of dead fish have been found since late July in the Odra, Poland's second largest river, which also runs through Germany. The exact cause of the mass fish die-off, which was labelled an "ecological disaster," remains unclear.