The environmental organization Greenpeace believes two coal and mining companies are responsible for the mass deaths of fish in the Oder last summer. A German-Polish team from Greenpeace took and analyzed 57 water samples from three tributaries to the Oder and six tributaries to the Vistula, the organization announced on Thursday. After the investigation, she assumes that wastewater from the mining industry was the trigger for the fish kill in the German-Polish border river. In three mines of two Polish companies, the pollution from saline discharges could be proven, Greenpeace said.

Experts assume that salt discharges were a major reason for the Oder fish die-off, combined with low water, high temperatures and a toxic species of algae.

The company Jastrzebska Spolka Weglowa S.A. (JSW) told the DPA it wanted to look into the Greenpeace report. In addition, coal producer JSW did not comment on the matter on Thursday. The second company has not yet responded to a request, nor has the Polish Ministry of the Environment.

Greenpeace further said: "Only through adequate monitoring by Polish authorities can further ecological catastrophes in the Polish-German river be prevented at any time." At the same time, it was said that the Vistula was more polluted by salt discharges than the Oder.

Federal Environment Minister Steffi Lemke (Greens) spoke of an environmental disaster on the Oder last summer. It is estimated that at least 360 tons of fish died on the Polish and German sides in August. Even months after the fish died, increased salt levels were measured in the river. Water experts are urging that salt discharges be quickly limited and warned that otherwise there could be another fish kill in summer. With federal funding, German scientists are now investigating the consequences of the massive fish kill and want to develop early warning systems.