Health officials in Oxford are advising swimmers to stay out of the water at Pittock Reservoir.
High levels of E. coli bacteria have been found in the recreational body of water prompting Oxford County Public Health to post a red warning sign that indicates the water is unsafe for swimming.
Swimming in waters with high levels of E. coli or other other disease-causing organisms, can cause skin, eye, ear, nose, and throat infections or gastrointestinal illness.
Health officials say the elevated presence of E. coli in the water is an indicator of fecal contamination from either animals or people, or both.
The beach will remain posted until test results indicate that the water quality meets the bathing beach water standard.
Water quality testing is conducted regularly on four Oxford area beaches and recreational lakes from June until Labour Day.
Last week, the main beach in Port Stanley was deemed unsuitable for swimming due to high levels of bacterial contamination.