Annual maintenance of the 131 Early Warning System sirens in San Luis Obispo County began Wednesday.
Each year, the sirens are inspected and tested one by one to confirm they are ready in case of emergency.
Sirens in Shell Beach, Avila Beach, See Canyon and Prefumo Canyon will be tested in the upcoming weeks, officials say.
Maintenance is scheduled between 7 a.m. and 6 p.m. on weekdays and between 8 a.m. and 6 p.m. on Saturdays.
Crews will sound each siren at low volume for a few seconds, officials say. Those near the sirens may hear the brief growl test.
If the sirens continue to go off, officials urge the public to tune to a local radio or television station for emergency information. In an emergency, the siren will sound for three minutes.
The sirens are located within the Emergency Planning Zone of the the Diablo Canyon Power Plant, a nuclear power plant owned and operated by PG&E. The zone stretches from the Nipomo Mesa north of Willow Rd. to Cayucos and includes the Five Cities area, San Luis Obispo, Los Osos and Morro Bay.
Officials say the maintenance will continue through July.
More information on the sirens and emergency preparedness information can be found at prepareslo.org.