“We have never had an operation of this scale in a river before,” said Monika Nowakowska-Drynda, a spokeswoman for the national fire service.
She confirmed that around 100 tons of dead fish had been pulled out since Friday.
The cause of their deaths remains unclear, but officials believe the animals were probably poisoned.
“A huge amount of chemical waste was probably released into the river, with full understanding of the risks and consequences,” Polish Prime Minister Mateusz Morawiecki said last week.
Water samples have been sent to laboratories in the Czech Republic, the Netherlands and Britain in hopes of finding the cause of the poisoning. The first reports about the mass loss of fish were received from Polish residents and fishermen as early as July 28.
German officials were surprised when a wave of floating dead fish appeared and accused Polish authorities of not informing them of the incident. In Poland, the government is also heavily criticized for its inability to react quickly.
In recent years, the Oder has been considered a relatively clean river; it is home to about 40 local fish species.
But now dead fish can be seen all over the river; some of them are up to 40 cm long. According to M. Nowakowska-Drynda, in Poland, more than 500 firefighters are pulling dead fish out of the water, using dams, boats, four-wheelers and even a drone.