A bomb disposal squad was sent in to a defunct nuclear power plant at Sellafield after a routine inspection discovered hazardous chemicals on the site.
During a routine inspection of chemical substances stored at Sellafield, a small amount of organic peroxide, a flammable and explosive material, was found.
The substance was being stored in the site's Magnox Reprocessing Plant, which was evacuated after the hazardous chemicals were discovered on Thursday.
A statement from Sellafield said the plant is non-operational while the chemicals are being dealt with.
"The storage area is safely segregated from the nuclear operations of the plant and the risk has been identified as a conventional safety issue rather than a nuclear safety risk.
"As a precautionary measure, a controlled evacuation of the Magnox Reprocessing Plant was carried out yesterday in order to investigate the chemical and devise the appropriate course of action.
"The plant was non-operational at the time. The plant will remain non-operational while the chemical is disposed of."
Sellafield no longer generates nuclear power. Instead, the site focuses on nuclear waste storage and nuclear decommmissioning.
