The Environment Agency says it is confident it has identified the source of an oil spill which threatened the lake at Clumber Park.
A suspected leak from an oil tank near the River Poulter led to a significant amount of diesel entering the river.
The pollution initially threatened a Site of Scientific Interest and the nearby National Trust lake at Clumber Park, but a report from a member of the public and swift action from the on-call Environment Agency team managed to stop the diesel before it drifted that far downstream.
The focus of the Environment Agency operation to deal with this incident is currently taking place at Carburton in Nottinghamshire, where booms have been set up across the river to contain the diesel, and absorbent pads have been brought in to start the clear-up process. It is expected that the operation will continue into the weekend.
The landowner of what is believed to be the source of the leak will, if proven, be charged for the clean-up operation and could also face legal action depending on the result of the investigation.
Paul Reeves, Environment Officer, at the Environment Agency said: “We have contained the pollution for now with the booms we have put out across the river so we can now concentrate on the clean-up.
“As a result of the extensive investigations we have carried out, we are confident the source of the diesel has been identified. We are now carrying out some tracing work to confirm this and, during this time, members of the public may see the River Poulter at Carburton slightly coloured with a green dye. This is a harmless substance and they should not be alarmed.
“It is hard to judge the environmental impact at this point, but as diesel generally sits on top of the water, the aquatic life below should be unaffected. However, we will be keeping a close eye for wildlife that has come into contact with the oil and the riverbanks for any effects.”