Thousands of dead fish have been discovered in the River Oder that separates Poland and Germany. Despite weeks of investigation, experts from both nations have not been able to determine the exact cause. Scientists believe that a chemical contamination that resulted in the water’s high salt levels may have occurred. The fish were harmed by the toxins that the golden algae released as they increased in number. The rotting bodies then significantly reduced the quality of the water. Andrzej Kapusta of the Inland Fisheries Institute expressed worry that it could happen again, especially if the original source of the pollution is still unclear.

In March, locals in a tiny marina first saw fish dying and the water changing. The owner started her own investigation when it happened again in June. This led her to believe that “someone dumped chemicals into the port.” Investigators are checking nearly 60 of the approximately 300 unregistered outflow pipes in relation to the fish deaths. While workers near Szczecin, Poland, remove gigantic dead carp and catfish from the river, a pump is desperately trying to add oxygen to the water. From here, the river flows on to a lagoon and the Baltic Sea. The volume of water may lessen the toxins, but there are concerns that what some people refer to as a “wave of poison” may continue its fatal route downstream.