Fish stocks have virtually disappeared from a stretch of the River Trent after it was polluted with cyanide.
A survey of the river between Stoke on Trent and Yoxall by the Environment Agency (EA) found, 'almost no evidence of living fish'.
In the main River Trent EA officers discovered just two solitary brook lampreys alive. These are likely to have survived because they bury themselves in sediment.
Only last year, the River Trent had been restocked with 40,000 young fish in an attempt to boost fish numbers following decades of industrial pollution.
The cyanide is believed to have entered the river through the Strongford Sewage Treatment Works in Stoke-on-Trent.
EA officers pumped oxygen into the river in an attempt to reduce the effects of the pollution but 'thousands' of fish were still killed.
The Agency said it was now investigating who was responsible for leaking the chemical and would prosecute them.
Red Industries Ltd, a waste management company, has been temporarily banned from dumping any industrial effluent into the water system. However, it has not been named as the source of the cyanide leak.
In 2004, Avonmouth-based chemical company Sevalco was fined £240,000 for deliberating discharging cyanide into controlled water.