People were warned to stay away from a river as thousands of fish were found dead after a deadly mix of cyanide and sewage leaked into a 30 mile stretch of the River Trent in Staffordshire.
The problem began on Monday last week after cyanide entered a sewage treatment works in Stoke through the pipe network that serves the plant from the city's 300,000 homes and businesses.
Since then the Environment Agency have been working to minimise the effects of the leak including pumping oxygen into the river to minimise the effect of the pollution.
Sewage works damaged
The cyanide killed the bacteria used in the sewage treatment process at the Strongford Sewage Treatment Works in Stoke-on-Trent, with the result that partially-treated effluent was discharged into the river.
This contained 'one part in a million' of cyanide and as the cyanide has cleared it has become clear that over several thousand fish were killed including pike, bullheads, perch, dace, barbel, chub, minnows and stickleback.
The Environment Agency website states: There were over a thousand dead bullheads alone.
The barbel ranged from 10 ounces to six pounds in weight, the chub weighed up to two pounds each, the dace up to six ounces, the perch to over a pound, and the pike were up to five pounds in weight.
Now that the pollution has subsided enough for officers to get on the river with their boat, they plan to carry out a full survey to try to establish how many fish died in this incident.
The Agency plans to investigate the incident fully and prosecute those responsible. It has already issued a suspension notice to prevent Red Industries Ltd of Burslem, Stoke-on Trent, from discharging any industrial effluent after tests showed the presence of cyanide at the sewer discharge point used by the company.
The news of the leak was met with dismay by anglers who together with the Angling Trust have invested huge amounts of time and money into water quality and habitats around the River Trent.
Just last year, the Environment Agency lead a restocking operation which involved nearly 40,000 fish including barbel, dace and roach being reintroduced into the river.
Ironically, the leak has occurred just a few weeks after the Angling Trust launched a specific campaign, in partnership with WWF and the HSBC Climate Partnership, to address surface water run-off from Birmingham causing pollution downstream.
There were significant fish kills in July this year on the River Tame, a tributary of the Trent, and on the main river itself after thunderstorms over the city flushed pollutants into the river.
Last month Severn Trent Water was fined nearly 10,000 when a sewage works overflowed into the river.