A detection of radioactive contaminants at the Vermont Yankee nuclear power led to a brief evacuation of 25 workers.
The incident happened Monday while the cover of a reactor vessel was being removed for refueling.
Entergy Nuclear spokesman Rob Williams says the cover was placed too close to a fan, which spread airborne contaminants.
Williams says the workers were evacuated from the top floor of the reactor building but returned about four hours later after they were checked for exposure to radiation.
William Irwin, of the Vermont Department of Health, says there was never any issue of public health being harmed.
A spokesman for the federal Nuclear Regulatory Commission says it is following up on the event but not investigating.