More than a thousand fish have been killed in Haverhill’s Stour Brook as pollution was discharged into the river.
The incident occurred at Stour Brook alongside Motts Field and East Town Park on Tuesday.
Environment Agency workers were on the scene quickly and worked through the night to re-oxygenate the water and rescue live fish.
They were also involved in the removal of dead fish. More than a thousand fish died from lack of oxygen caused by the pollution.
A spokesman for the Environment Agency said: “We are aerating a stretch of the Stour Brook after hundreds of fish died from lack of oxygen caused by pollution.
“We are investigating the cause of the pollution and carrying out a survey of live fish to see if they need to be rescued from the water.
“The local authority has been notified and dog owners are being advised to keep their animals from the water. Abstractors downstream have also been informed, he said.”
It was anticipated that, as the pollution moves downstream and is diluted by yesterday morning’s rainfall, the impact of the pollution will lessen.
Two dogs have already been taken to a vets at Haverhill as a result of the pollution.
The Environment Agency is currently conducting an investigation into the leak and how it occurred.
Staff are concentrating on a 4km stretch of the River Stour.
Members of the public should call 0800 80 70 60 for further information.