Concern has been raised after three dead sheep were seen floating in the River Nene.
The animals were spotted in water next to the top lock on the Embankment in Wellingborough earlier this week.
Annie Marriott from Animals In Need nearby was appalled to come across the animals.
She is a trustee of the charity which rescues and re-homes hundreds of animals each year and is based at Pine Tree Farm, just a 10-minute walk away from where the sheep were discovered.
Annie believes all the sheep drowned, and added: “People use this stretch of river to pass through Wellingborough on canal boat holidays so who knows what they must think as they pass through.”
A spokesman for the Environment Agency said: “We understand that seeing deceased animals can be upsetting, but in this case the sheep aren’t posing a risk to the environment either in terms of causing pollution or posing a flood risk by blocking the flow in the channel.
“But as always, if people spot something they think is of environmental concern, we’d ask them to call our incident hotline on 0800 807060.”
The Northants Telegraph also contacted the RSPCA about the sheep but a spokesman said the matter had not been reported to them.