Kilsyth’s Garrell Burn is being polluted by raw sewage entering the waterway.
A Kilsyth resident, who has requested anonymity, alerted authorities to the problem.
The pollution is entering the water not far from St Patrick’s Primary School.
The contact told the News and Chronicle: “I walk my dog in the area and realised there was a problem near the old slaughterhouse bridge.
“I found where the pollution was getting into the water and was able to identify it as raw sewage.
“Not only is this water near a school, but this area is a nature reserve and the pollution is harming wildlife.”
The caller believes the problem is linked to the new Barrie Way housing estate, but as yet this has not been confirmed.
A spokesperson from the Scottish Environment Protection Agency (SEPA), said: “SEPA is aware of pollution which has entered the Garrell burn close to Kilsyth.
“Discussion have taken place with Scottish Water to ensure that the discharge is rectified as quickly as possible and SEPA will continue to monitor the situation in order to gauge what impact, if any, the pollution might have on the local environment.”