Polish authorities have found toxic golden algae in the Oder River along the border with Germany.

The golden algae entered the river from the Gliwice Canal, the Poland's climate and environment ministry said on Friday evening.

The highest risk level has been set in a part of the river near the town of Lanai, southeast of Wroclaw.

In the Gliwice Canal, which flows from the Oder, many dead fish have been found since last week. According to experts, goldfish do not do as well in the Oder stream as in the canal's stagnant waters.

However, an additional risk factor was the drop in the water level of the Oder at the beginning of May. The Gliwice Canal, opened in 1939, is 41 km long and connects the town of Gliwice in Upper Silesia to the Oder.

In the summer of 2022, the Oder also started to see a mass of fish. German and Polish experts then concluded that the fish plague was probably caused by toxins released into the water by the rings of the poisonous golden algae Prymnesium parvum.

Now the crisis management team wants to ensure that the number of golden algae that have been introduced into the Oder is kept to a minimum.

To this end, the Polish Water Inspectorate has been instructed to open the canal's sluice gates as rarely as possible and to control the water flow accordingly. In addition, the condition of the soil along the banks of the river is regularly monitored.