Firefighters quickly responded, setting up a protective barrier to prevent the spread of possible pollutants near the eastern town of Bohumín.

Police have also launched a criminal investigation to determine the cause of the die-off.

“Officers are analyzing water samples to pinpoint the substance or condition responsible,” police spokeswoman Pavla Jiroušková confirmed.

Environmental specialists are exploring several possible triggers, including industrial pollution, agricultural runoff or natural phenomena like oxygen depletion.

Authorities have intensified inspections of nearby factories and farms to ensure compliance with environmental regulations.

Aquatic ecosystems like the Oder River are essential for biodiversity and ecological balance, with disruptions potentially rippling through the food chain, threatening both wildlife and humans.

Local environmental groups and residents are now demanding swift action to address the disaster and prevent a repeat.