- At least 300 tons of dead fish have been recovered from the Oder river.
- The cause is still not apparent, but analysis indicates toxic algae and high salt levels could have played a role.
- Germany's Environment Minister Steffi Lemki described it as an "environmental disaster".
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At least 300 tons of dead fish have been recovered from the Oder river that runs through Poland and Germany since fears were raised of a chemical spill there in July, according to the German environment ministry.
"We are currently experiencing an environmental disaster that will damage this valuable ecosystem for a long time," German Environment Minister Steffi Lemke told news website The Pioneer on Thursday.
Out of the 300 tons of dead fish recovered, some 100 tons were pulled out in the German state of Brandenburg alone, the report said, citing figures from the environment ministry.
Fishermen in Poland first started reporting dead fish in the Oder in late July and they began washing up in Germany a few days later.
The cause of the disaster remains a mystery, though analysis of water samples has suggested toxic algae and high salt levels could have played a role.
READ | Mass fish die-off in german-Polish blamed on unknown toxic substance
Berlin has accused Warsaw of failing to communicate the problem, while Poland has slammed Germany for spreading "fake news" about the discovery of herbicides and pesticides in the water.
Germany said this week that lab results from the Leibniz Institute and the University of Vienna had shown the presence of a toxic brackish water algae in the Oder.
However, a German environment ministry spokesman said the formation of such algae is "not a purely natural phenomenon" and "does not occur to this extent... under natural conditions".