A large fish kill in the Oder worries anglers and authorities in Brandenburg on the border with Poland.

Thousands of dead fish were discovered in the river, some of them near the city of Frankfurt (Oder) and surrounding towns.

The public prosecutor's office in Wroclaw (Breslau) is investigating a possible environmental crime.

Did toxins get into the water on the Polish side?

The exact cause of the massive fish kill has so far remained unclear.

However, a Polish authority found a toxic substance in two places.

But the investigations should continue.

In addition, criticism was heard that the flow of information was not good enough.

An ecological tragedy

The city of Frankfurt (Oder) and the districts of Märkisch-Oderland and Uckermark recommended on Wednesday to avoid contact with the Oder water and water from the Hohensaaten-Friedrichsthal waterway and not to eat fish from the river.

In addition, it was advised not to use the water for drinking troughs or irrigation.

The Märkisch-Oderland district wrote that the fish die-off has been observed in the Oder between Finkenheerd and Genschmar since recently.

According to the Polish media, the first reports of anglers who had found dead fish on the shore came out at the end of July.

According to the authorities, there are now thousands found, first in Lower Silesia, but now also in the Lubuskie Voivodeship further north.

Anglers who fished tons of dead fish out of the river spoke of an "ecological tragedy".

Mesitylene detected

According to the reports, inspectors from the water authority in Lower Silesia had already taken water samples from three places at the end of July.

According to the analysis, the high oxygen content in the water deviates from the typical oxygen concentrations in summer.

It is possible that a substance with strong oxidizing properties got into the water, the authority announced in early August.

In addition, the toxic substance mesitylene was detected in two places.

The result of further analyzes is still awaited, said a spokesman on Wednesday.

Marek Cebula, the mayor of the village of Krosno Odrzanskie, called on the city's residents on Wednesday to avoid the banks of the Oder and in particular contact with the water until the cause of the fish kill was clarified.

"We have not received any official notification of contamination of the Oder," he wrote on the city's website.

It is regrettable that the mayors of the Oder cities were not informed by the responsible authorities.

"A proper flow of information is worth its weight in gold here."

Intransparent information situation

So far, there is no reliable information about the causes and the concentration of any pollutants in the different sections of the river, according to the city of Frankfurt (Oder).

The authorities are currently examining the background.

"I expect a speedy clarification of the incident.

The non-transparent information situation is particularly frightening," said Left Party MP Christian Görke.

"Many people use the Oder and the adjacent meadows and islands such as the Ziegenwerder for recreation and at the current temperatures, dogs and people sometimes go into the water to cool off." The exchange of information between Poland and Germany at federal and state level must be clear here get better to warn people in time.

Already at the end of July a large fish kill

The Greens member of the state parliament Sahra Damus from Frankfurt (Oder) questioned whether the reporting chain and the German-Polish disaster management worked well in the 25th year after the flood of the century.

That would have to be clarified at a later date, she said.

"In our view, the priority now is to clarify the causes and contain this ecological catastrophe on both sides of the Oder as quickly as possible."

The chairman of the BVB/free voters parliamentary group in the Brandenburg state parliament, Péter Vida, said that the Polish authorities had already become aware of a large fish kill at the end of July.

However, no precautions had been taken and the authorities were groping in the dark as to the cause.

"The incident shows that Poland and Brandenburg need to improve cross-border cooperation and communication between their authorities," Vida said.

"Because with an advance warning of several days, at least some of the damage could have been prevented."