Routine liquor level monitoring on the Sellafield site has indicated there may have been a recent leak from the Magnox Swarf Storage Silo, a legacy storage facility which is a priority for decommissioning.
A spokesperson from Sellafield Ltd said: "In the 1970s there was a confirmed leak at the same plant and recent data suggests that this may have reoccurred. This was always a known risk that we have prepared for and regulators have been notified.
"The building is partly sited underground, the area of the suspected leakage is also below ground and therefore there is no health risk to the workforce.
"Movement of radioactive material through the ground takes many years and there is also no health risk to the local community.
"At Sellafield, we have a well developed programme of monitoring of the underground environment. There has been no change to conditions presently detected as a result of this suspected leakage. A well established management plan is being followed to continue to monitor the current situation.
"Contamination created as a result of leakage will be dealt with in line with the current ground remediation plan for the area surrounding the Magnox Swarf Storage Silo, once it is fully decommissioned.