People are being warned to keep away from the water and water’s edge at a county site after toxic algae was found there.
Routine water sampling by Environment Agency officers has identified a toxic blue-green algae bloom in the lake at The Washlands, Northampton.
The algae is visible on the water’s surface and could cause serious illness in humans and animals.
The Environment Agency has put up warning signs along the lake to alert the general public and dog walkers are being asked to keep their dogs out of the water.
An Environment Agency spokesman said: “Blue-green algae produces toxins which can harm, or even kill, farm animals, pets and wild animals, and cause skin-rashes, eye irritation, vomiting, diarrhoea, fever and muscle and joint pain in people.
“Environment Agency staff will regularly test water samples from the affected area and warnings will remain in place until the algal count drops to a safe level.”