A small amount of radiation has been detected in a reactor building at the Three Mile Island nuclear power plant in central Pennsylvania.
About 150 employees were sent home after the radiation was detected Saturday afternoon, but officials say there is no public health risk.
Exelon Nuclear spokeswoman Beth Archer says investigators are searching for the cause, but that the radiation was quickly contained.
Radiological surveys showed the contamination was confined to surfaces inside the containment building.
The unit has been shut down for refueling and maintenance since Oct. 26. The company hopes to resume activities Sunday.
Officials are checking employees who had been working in the building for possible unusual radiation exposure.
A partial meltdown occurred in Three Mile Island's Unit 2 reactor in March 1979.