Environment Agency officials say they have managed to trace the source of the pollution affecting the River Wye in Buxton.
An investigation is continuing after a detergent entered the water course, resulting in a white foam being visible along a one-mile stretch of the river.
A spokesperson for the Environment Agency told the Advertiser on Monday: “Severn Trent Water have now traced the source of the pollution and the discharge has now been stopped.
"However, it will take time before the foaming stops completely and we will continue to monitor the river for signs of any impact on the local wildlife and environment."
Speaking on Saturday, Kelly Golds, Area Duty Manager for the Environment Agency, said: “We are investigating this incident as a matter of priority and are working closely with Severn Trent Water to determine the source of the pollution.
“Our officers have been on site to take samples of the river and we do not currently believe that the local wildlife has been impacted.
“We will continue to work to determine the source of the pollution and we will be monitoring the river for signs of impact.”
Anyone who see signs of fish in distress is asked to report this to the EA’s 24/7 incident hotline on 0800 80 70 60.