Security personnel at a Massachusetts nuclear plant responded to the sound of gunfire Saturday morning, only to learn later that the shots came from duck hunters on adjacent land.

Before the source of the shooting was identified, the shift manager on duty at Entergy's Pilgrim nuclear plant activated the site's emergency plan and declared an unusual event at 9:50 a.m., according to a report filed with the Nuclear Regulatory Commission. Police and security personnel then tracked down the shooters in a small boat near the plant, and the event declaration was cancelled at 11:05 a.m.

The Boston Globe quoted local police as saying they confirmed that the two people near the plant were hunters and that they were in the area legally. The reactor, on Cape Cod Bay near Plymouth, was offline for repairs at the time.