During a routine inspection of chemical substances stored on the Sellafield site, a small amount of chemicals (organic peroxide) were identified as requiring specialist disposal.
This chemical is used for a variety of purposes across many industries.
A spokesperson from Sellafield Ltd said:
"In line with established procedures, support has been requested from Explosive Ordinance Disposal (EOD).
"The EOD team is now in attendance at the Sellafield site and will dispose of the chemical safely.
"Chemical monitoring is undertaken across the site to understand changing chemical states and to inform when and how industrial chemicals should be stored or disposed of.
"This chemical substance was stored in the site’s Magnox Reprocessing Plant. 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.