An investigation has been launched after 20 workers at the Dounreay nuclear plant in Caithness were contaminated with radioactive particles.

Routine checks detected contamination on the footwear of staff at a waste handling plant.

Subsequent investigations found two employees in the D2001 plant had radioactivity on their hands, while one of them also had traces on his face.

There was no radioactive release to the environment and there is no evidence that any of the workers ingested any radiation

UKAEA spokesman

They are due to undergo tests on Wednesday morning to re-assess their condition.

A spokesman for the UK Atomic Energy Authority (UKAEA) said: "They were taken to our occupational health unit where efforts were made to clean the particles from their skin.

"Most of the contamination was cleaned from their skin and they were sent home wearing rubber gloves.

"It is difficult to quantify at the moment but we believe the risk to them to be low."

The UKAEA said early indications suggested that the leak was confined to one floor of the building.

"The operation was stopped and the building was sealed off," he said.

Protective screens

"There was no radioactive release to the environment and there is no evidence that any of the workers ingested any radiation."

At the time of the incident 70 workers were carrying out decommissioning work using robotics arms to lift radioactive materials, which were shielded from them by protective screens.

The spokesman said an investigation had been launched to establish the cause of the incident.

The Health and Safety Nuclear Safety Inspectorate has also been informed and is expected to launch a separate inquiry.

Dounreay already has an appalling safety record and this incident comes against a background of leaks and safety problems

John Swinney, SNP leader

Dounreay was given a clean bill of health earlier this year following an audit by the Health and Safety Executive.

The review followed a number of safety lapses at the site in the late 1990s.

Scottish National Party leader John Swinney said the leak was "a matter of enormous concern".

Mr Swinney said: "Dounreay already has an appalling safety record and this incident comes against a background of leaks and safety problems".

He is seeking full disclosure of what he described as "this worrying failure in safety procedures" had happened.