More than x tons of fish have been found dead in a European river since late July — an unexplained "ecological catastrophe" that is inexplainable scientists and political leaders alike.

Germany and Poland are working together to solve the mystery backside the mass die-off in the river Oder, which flows between the ii countries.

Devastating pictures of the stricken fish were photographed from the Oder concluding calendar week, as Europe sweltered in a widespread and subversive heat wave.

"Our border river Oder has been hit difficult. The massive fish kill is frightening," Axel Vogel, agriculture minister for the German state of Brandenburg, said in a German authorities argument Monday.

"Nosotros have to fear that the Oder will have a long time to recover from this catastrophe. This is besides very bitter for Germany'due south only overflowing-plain national park, the Lower Oder Valley."

The Oder, known equally Odra in Shine and Czech, runs from Czechia to the Smooth-German border before flowing into the Baltic Sea. Information technology is one of the biggest rivers in Poland.

Environmental disaster on the Oder River
Fish deaths in the Oder River take been worrying locals for weeks. Patrick Pleul / DPA via Getty Images

The continent is suffering what experts say could be its worst drought in 500 years, with major rivers from the Danube to the Rhine drying up. And conditions are set to worsen in the weeks and months alee, they add.

While climate modify is non thought to be a main cause of the fish washing up dead in the Oder since July, experts have said that low levels of oxygen in the river — a upshot of unprecedented low h2o levels due to the heat wave — could accept played a role.

"Nosotros are dealing with a gigantic and outrageous ecological catastrophe," then-Polish Waters head Przemyslaw Daca said in a news briefing Friday.

The main cause is thought to exist water contamination due to a toxic substance, though officials take been unable to identify what it is.

People have been warned non to swim in the river nor to eat whatever fish from it. Shine soldiers and army reservists were called in over the weekend to assist a huge cleanup operation, Polish Defense Minister Mariusz Błaszczak said in a tweet.

So far removed more than than 10 tons of dead fish.

Local and national politicians from Deutschland and Poland met Lord's day and agreed to class a bilateral chore force, the German authorities's argument said. Leaders from both nations said they suspect human-made pollution is to blame.

"The top priority is protecting the population, limiting impairment and identifying the polluter," German Federal Environs Government minister Steffi Lemke said at a news conference post-obit the meeting Lord's day.

"Experts are working flat out on the assay in social club to notice out every bit quickly every bit possible which substances are causes of the mass death of fish and the damage to the Oder."

She added that by Sunday, at least 150 samples of h2o from the Oder River had been tested, but none of the studies had confirmed the presence of toxic substances.

"At the same fourth dimension, we are testing fish. No mercury or other heavy metals have been establish in them," Poland'south environment minister Anna Moskwa said at the same news briefing.

She said some Oder water samples were existence sent to foreign laboratories to be tested for some other 300 substances, including the presence of pesticides. She said on Tuesday that samples had been sent to the Czechia, Netherlands and the United kingdom of great britain and northern ireland.

Polish Prime number Minister Mateusz Morawiecki, whose correct-wing regime is under huge force per unit area to solve the mystery and stop more than fish from dying, said Friday that "huge amounts of chemical waste" were probably to blame, adding in a Facebook video that "nosotros will not residual until the guilty are severely punished."

On Friday, Morawiecki said he had fired Daca Przemysław, head of the national inland waters agency, and Michał Mistrzak, head of the full general ecology inspectorate, a regime agency that investigates environmental disasters, considering of their handling of the disaster.

Image: GERMANY-POLAND-ENVIRONMENT-ANIMAL-FISH
Government in the metropolis of Frankfurt warned "strongly" against coming into contact with the water from the river Oder. Odd Andersen / AFP - Getty Images

Huge numbers of dead fish were start spotted virtually the southwestern Smoothen town of Olawa in tardily July.

High german officials have complained that Poland failed to accolade an international treaty past not notifying them immediately nigh the possible contamination of the river.

A gunkhole helm beginning alerted German government about the dead fish on Aug. nine, Federal republic of germany'due south federal regime said.

"Nosotros know that the chain of reporting that's envisaged for such cases didn't piece of work," Christopher Stolzenberg, a spokesperson for Federal republic of germany's Federal Environment Ministry, told reporters in Berlin, according to the Associated Press.

NBC News has contacted the Smooth Ministry of Climate and Environment for comment regarding the allegation.