A Three Mile Island spokesman says steam was released this morning when the nuclear power plant automatically shut down, creating a loud noise heard by nearby residents.
Spokesman Ralph DeSantis says TMI was being manually shut down for repairs when it suddenly shut down by itself.
The steam was released as part of the shutdown, which is a safety measure and not a malfunction.
Officials say radiation levels in the steam posed no threat to public safety.
TMI will return to service after the repairs, inspections and testing are complete.