"WARSAW - Poison cannot be ruled out as the cause of a mass die-off of fish in the Oder river but tests so far have not proven toxic substances were to blame, Polish Environment Minister Anna Moskwa said on Sunday.

Tonnes of dead fish have been found since late July in the river Oder, which runs through Germany and Poland. Both countries have said they believe a toxic substance is to blame, but have yet to identify what it is.

"As of today, none of these (water) tests have confirmed the presence of toxic substances," Moskwa said after meeting with her German counterpart and other German and Polish officials."

Anna Koper and Jan Lopatka report for Reuters August 14, 2022. [2]