A section of the nuclear facility, Sellafield, has been evacuated after dangerous chemicals were found during a routine inspection.
An explosives disposal team has been called in to assist the incident, at the Magnox Reprocessing Plant, after a small amount of organic peroxide was identified.
The chemical, which is widely used across many industries, can be potentially hazardous if not stored at the right temperature.
The site alerted the Explosive Ordnance Disposal team who are now on site to remove the material safely.
A statement from Sellafield said: "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.
"As ever, our priority remains the protection of our workforce, community and the environment."
More on this as we get it.