The Environment Agency is working to contain a cyanide spillage at an industrial estate.
Around 1,000 litres of diluted cyanide spilled after a forklift truck pierced the container carrying the toxic chemical.
It happened at a business in Heanor Gate Industrial Estate, in Adams Close, Derbyshire on February 6th.
Seven people were decontaminated at the scene
Some of the hazardous liquid leaked into a nearby brook, which runs to Shipley Country Park.
Derbyshire Fire and Rescue Service said there is no risk to the public as the cyanide was heavily diluted at a concentration of 2%.
A spokesperson for the Environment Agency said: