Environment Agency officers have been working at Adam’s Pond in Heanor all weekend following an accidental chemical spill.
Staff have been monitoring the situation, taking samples and taking steps to reduce the impact of water contamination.
On Saturday, a spokesman said: “Our sample results show that the toxicology levels in the water are low and do not pose a significant risk to the birds, through direct contact with the water or from eating the dead fish.”
The accident happened on Tuesday, February 6, when around 400 litres of liquid cyanide were spilled at a nearby industrial unit on Adams Close.
Environment Agency officers were immediately on the scene along with colleagues from Derbyshire Fire & Rescue Service, Severn Trent Water and Derbyshire County Council - which owns the Shipley Country Park site.
Large numbers of dead fish have been spotted in the water, and heavy rains have increased the risk of pollution spreading.
Environment Agency area manager Penny Thorpe said: “A temporary dam has been created in order to stop the spillage leaving the pond and to prevent any further contamination and our officers will continue to monitor the environment for any other impacts from this spillage.”
Walkers have been advised to steer clear of Adam’s Pond and Osborne’s Pond as a precautionary measure.
Anyone encountering signs of pollution should call the agency’s hotline on 0800 807060.