The mystery of what caused the death of 100,000 fish in the River Nene near Peterborough last month will not be solved after an investigation drew a blank.
Fish were found washed up on the river bank between Orton Backwater and Goldie Backwater, and in Ferry Meadows park, on 12th December.
The Environment Agency tried to establish the contaminant, after removing the sewage.
“We believe that the pollutant that had a significant effect on the fish passed through for a short period of time and so we were unable to trace the source,” it said.
It said its officials had spent hours over the past few weeks taking samples and visiting a large number of locations.
“Our investigations did not uncover any further damage and we are now observing the normal behavior of the fish,” added a spokesperson.
“We plan to conduct fish population surveys to establish the status of fish stocks, which will determine the need to potentially restock parts of the river.”
At the time, Chris Park, of the Nene Park Trust, which runs Ferry Meadows, said the sight of washed-up bodies was “sickening”.
The trust fears the fish die-off could have a “devastating impact on future breeding”.
The agency said it had fast-tracked river samples amid efforts to establish the cause.
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