The Environment Agency is investigating reports of pollution caused by the renovation work at Wicksteed Park’s lake.
Silt from the lake leaked into the River Ise on Tuesday, September 17.
An Environment Agency spokesman said: “We investigated the reported incident and confirmed the source of excessive silt in the River Ise.
“Pollution control materials were installed that helped the river be free of silt and flowing smoothly by the evening of September 19.”
The park says the project is being carried out in consultation with relevant authorities.