Members of the public are being urged to come forward with information about a pollution incident that killed thousands of fish in a Bolton brook.

The Environment Agency has launched an investigation after around 10,000 fish were found dead along an 11 kilometre stretch of Eagerly Brook in Belmont. The fish were mainly mature brown trout, some of which weighted up to 3lbs, but there were also a number of smaller fish including sticklebacks.

Rumours that the pollution had killed fish in Belmont Valley Fishery and the Ornamental Reservoir are not true.

The alarm was first raised last Tuesday evening (12 September) when a member of the public reported seeing a blue liquid and foam in the brook. A separate pollution incident was reported last Wednesday afternoon (13 September).

A team of 10 environment officers and fisheries officers supported by staff from United Utilities attended the scene to carry out tests and launch a clean-up operation.

Water quality samples have been taken and are being analysed by scientists in the Environment Agency’s laboratory in Nottingham. The results are expected early next week.

Steve Richardson, the lead investigator for the incident, said: “We suspect that the first incident was caused by somebody illegally dumping a chemical or toxin into the brook while the second incident seems to have been caused by someone emptying the contents of a septic tank and/or chip fat or into the brook.

“This irresponsible action has proved deadly to the fish and it could take years for the river to recover.

“We are determined to find the culprits and are appealing to anybody who has seen or heard anything that could help us with our investigation. One member of the public reported a van pumping waste into a manhole and we are particularly keen to speak to the owner of this van.”

Anyone with information is encouraged to call the Environment Agency for free and in confidence on 0800 80 70 60.