A nuclear power plant warning siren went off by mistake Sunday, scaring hundreds of residents who blocked an emergency phone system for 20 minutes, authorities said.
The siren, one of 52 within a 10-mile radius of the San Onofre nuclear power plant, sounded at 1:12 a.m., letting out an undulating wail for 4 minutes and 28 seconds until its power was disconnected by a technician for the plant, said David Barron, a spokesman for Southern California Edison Co.
The plant was operating normally Sunday and company technicians were investigating the mechanical malfunction that set off the siren at the Salvador Peak communications site, Barron said.
It took almost an hour for two local news sources to announce the false alarm. In the meantime, residents within half a mile of the siren swamped local 911 emergency lines.
Police received calls from more than 400 residents, Sgt. Steve Bernardi said.