The U.S. Nuclear Regulatory Commission says the small amount of radiation detected at the Three Mile Island nuclear power plant is not significant.
Specialist John White has told ABC News on Sunday that there is no indication that radiation at the plant exceeded or even approached regulatory limits.
The commission sent investigators to the central Pennsylvania plant after a small amount of radiation was detected.
About 150 employees were sent home Saturday afternoon, but officials say there is no public health risk.
Exelon Nuclear spokeswoman Beth Archer says the radiation was quickly contained.
The unit has been shut for refuelling and maintenance since Oct. 26. Workers are being tested for radiation exposure.