No evidence Odra fish deaths due to sewage - environmental chief

An investigation into the circumstances surrounding the death of thousands of fish in the River Odra this summer has found no abnormalities in sewage discharge into the river, an environmental official said on Thursday.

Around 200 tonnes of dead fish were recovered from the Odra, Poland's second longest river, in July and August in one of the worst environmental disasters to strike the country in recent years.

Andrzej Szweda-Lewandowski, director general of environmental protection, told a press conference held to present a preliminary report into incident that the entities permitted to release sewage into the Odra are currently being analysed.

"There are very many entities, around 500," he said. "Investigations conducted to date, analyses of the... permit protocols... show that none of the investigated entities have discharged abnormal sewage," he said. "All discharges that occurred, that have been investigated so far, have been in line with the legal permits."

As a result, he added, it was not possible to conclude that a substance discharged into the river along with the sewage had 'caused this catastrophe."

The geographic distribution of the fish deaths, said Szweda-Lewandowski, also precluded the poisoning theory.

"In large stretches of the river's current no deaths at all were recorded, but deaths were recorded in... stretches of an oxbow lake," he said. "So not in the current but to the side, in a river basin."

If a poisonous substance had been responsible, he continued, the deaths would have occurred along the river's entire length, more or less evenly.

He said the "hydromorphological specifics" of oxbow lakes may have been the cause of, or a contributing factor in, the mass die-offs as there had been algae blooms in those locations but not in the riverbed itself.