LONDON Jan 31 Britain's nuclear reprocessing site Sellafield said on Friday that elevated levels of radioactivity were due to naturally occurring background radon, and not any issue with its operations.
"Our in-air monitors are extremely sensitive and pick up on any abnormality," it said, in a statement on its website.
"Overnight the monitoring system initially indicated elevated levels of activity. Following investigation and analysis, we can now confirm these levels to be naturally occurring background radon."
The site had earlier told non-essential staff to stay away from the site.