Britain's Nuclear Decommissioning Authority (NDA) said it was too early to know if a leak was the cause of elevated levels of radioactivity detected at the Sellafield nuclear reprocessing plant.
"It is far too early to say there is a leak," Bill Hamilton, a spokesman said. "Everything being done is precautionary. There is no danger to the workforce, communities or wildlife. At the moment we don't know where the radiation is coming from."
The NDA is a public body that reports to Britain's energy ministry.