A radiation leak in the eastern US state of Pennsylvania has forced the evacuation of about 150 workers. The leak occurred Saturday afternoon at Three Mile Island, the scene of the worst US nuclear power plant accident in 1979.

One employee was found to have received 16 millirems of exposure, or the equivalent of about three X-rays. Other workers were exposed to lower levels. Officials said on Sunday there was no threat to public health or safety.

Investigators are trying to determine the cause of the radiological contamination inside the nuclear facility's building.