Discharges from the Polish mining industry apparently caused fish deaths in the Oder last summer. According to a report published by Greenpeace on Wednesday, scientists were able to detect salt discharges in three tributaries of the Oder in the Silesia region.

According to this, three mines of the mining companies Polska Grupa Górnicza and Jastrzebska Spólka Weglowa, which operate mines there, are responsible for this. Downstream, salinity rose sharply, according to the report.

In July and August, fish and mussels died in the Oder over a length of 500 kilometres due to a toxic algae. Hundreds of tons of fish had to be recovered. The brackish water algae was able to spread, especially due to the high salinity of the river.

For some time, the wastewater of the mining industry had been suspected of having caused the disaster. So far, however, it was unclear where the salty water came from.

The report by the german-Polish Greenpeace team is based on water samples from August, November and December. The Leibniz Institute of Freshwater Ecology and Inland Fisheries had already published a report at the end of November, according to which the river continued to have too high salinity.