An investigation is being carried out into the origins of around 200 litres of oil that spilled into the Erewash Canal at Long Eaton.
The pollution was spotted on Thursday by a member of the public and led to a clean-up operation by the Environment Agency.
Investigations began on Friday into the cause of the spill at the stretch of the canal close to Bennett Street. These continued at the start of this week as the source of the pollution was narrowed down.
A spokesman for the EA said there was no significant spillage over the weekend and a officer had checked and replaced the booms (that stop oil flow) as a precaution.
He said: “The incident was reported by members of the public who saw the oil in the water between Long Eaton and Toton on Thursday evening
“Officers, including Paul Reeve went to investigate late afternoon and established it was oil.
“He went back on Friday morning and deployed booms to stop the spread and pads from a small watercourse that leads into the river to absorb the oil.”
The clean-up involved officers in the cold water using the pads to soak up the oil. Samples were taken for analysis.
On Friday, Paul Reeve tweeted: “Our #opsdelivery team are currently busy cleaning up the #oil in #LongEaton #Derbyshire with absorbent booms and pads.”
Following investigations the source has been narrowed down to business premises along Bessell Lane.
Anyone who wants to report pollution can call the Environment Agency on 0800 807060.
Further investigations will be taking place this afternoon (Monday).