A 25km stretch of the river Great Ouse, which runs through Buckingham, has been polluted by a chemical spill, killing hundreds of fish.
At the weekend, residents in Buckingham began to report that the river had turned into a 'bubble bath' and had a strange smell.
The Environment Agency (EA) have said there is nothing they can do to remove the pollutant and that it will dilute as it moves downstream.
EA add that while they are assessing the impact people should keep their dogs away from the foamy water and refrain from fishing.
The problem is believed to have began after a fire at an industrial unit in Brackley on the evening of Tuesday 26th June, raising questions as to how the contaminant, said to be detergent, entered the river.
Buckingham councillor Robin Stuchbury said: “The river was pristine clean – one incidence of pollution may have set us back 20 years,” adding “in this day and age we shouldn't be using the river as a sewer.”
If members of the public see any large areas of foam or smell anything unusual in the river they are advised to contact the Environment Agency emergency hotline number: 0800 80 70 60.