The five had been handling a package of uranium waste when it ignited and firefighters were called in to extinguish the blaze.

A spokesman for the north of Scotland plant said the five workers were in a waste handling area of the plant when the fire broke out in a small package containing what was described as "low level waste".

Five workers are being monitored

"The area was immediately evacuated but has now been re-entered to confirm that the fire is extinguished and the situation is now under control," he said.

However, he added: "Although there is no evidence of contamination, as a precaution the five staff involved will be checked to confirm that there was no intake of radioactivity."

And checks may be extended to other people at the plant "as necessary".

The Government last year announced plans to wind down the plant, which has been dogged by a string of controversial incidents over the past 18 months.

In May 1998, the Government's environmental watchdog in Scotland announced it was to curb radioactive pollution levels at Dounreay.

The Scottish Environmental Protection Agency (Sepa) acted after Dounreay officials admitted miscalculating radiation levels.

They revealed that levels of radioactivity at Dounreay over the previous six months had been up to 10 times higher than those reported. But they stressed they were still well below authorised limits.

Safety review

In May 1998, the Health and Safety Executive revealed a sweeping safety review of the Dounreay plant.

The inquiry followed an incident when a digger cut through electrical cables, paralysing the plant after the emergency supply also failed, prompting concerns about the control of the plant. And in June 1998, the UK Atomic Energy Authority admitted that 170kg of weapons-grade enriched uranium had disappeared from Dounreay - enough to make a dozen atomic bombs. The loss of the uranium was discovered a few months after the Government announced that a contaminated waste shaft would need cleaning up in a 25-year operation costing up to �355 million.