Restrictions have been placed on gathering seafood and bait from a beach affected by radioactive particles.
Warning signs are already in place at Dalgety Bay in Fife saying seafood should not be collected but new restrictions have been issued making it an offence, the Food Standards Agency in Scotland said.
The move is "a precautionary measure" following recent surveys detecting radioactive items on the beach, the food watchdog said.
It added that the restrictions will be reviewed in light of further evidence or any action taken "to remediate the contamination".
Although there is no commercial fishing or shellfish industry in the area, individuals are known to collect shellfish, it said.
Radioactive material was first detected on the foreshore of Dalgety Bay in 1990.
The contamination is thought to stem from residue of radium-coated instrument panels used on military aircraft which were incinerated and put in landfill in the area at the end of the Second World War.
A lump of contaminated metal was found on the beach in October last year, prompting the closure of part of the foreshore.
In April, an investigation plan to establish how to clean up the beach was agreed by the Ministry of Defence (MoD) and the Scottish Environment Protection Agency (Sepa).
The MoD's final Dalgety Bay inspection plan was published by its Defence Infrastructure Organisation and Sepa.
The environmental body said it expects "remediation action to follow urgently" at the conclusion of the investigation.
The timescale for completing the five-stage plan, which includes surveying the area, sampling and analysis, is May 2013. However, the report states "the intention is to complete each investigation stage as quickly as possible".
The Dalgety Bay Particles Advisory Group, set up by Sepa, met for the third time today to hear about the work being carried out recently.
Alex Elliott, the group's chairman, said: "We expressed our continuing concern at the continuing discrepancy between MoD's contractor's monitoring and that undertaken as a check monitoring by Sepa.
"We have clarified that all radioactive particles detected using the established protocol should be removed from the beach irrespective of their depth. We trust that this will allow appropriate monitoring of the beach to occur whilst the MoD seek to determine the extent of the problem and develop the appropriate remediation options."
He added: "We were also informed of the action taken by Food Standards Agency and welcome this as it will provide further protection to the public whilst key information to allow a robust risk assessment to be undertaken is collected".
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