Since last Tuesday, 11 possible cases of E. coli have been reported to HHSA, the agency reported. E. coli bacteria can cause abdominal cramping, bloody diarrhea, vomiting and nausea.
Anyone experiencing these symptoms is advised to call a doctor.
The source of the bacteria has not been identified, but the Southern California restaurant chain, Pat & Oscar's, confirmed that it has been contacted by HHSA in connection with the investigation.
The chain, which has restaurants in Carlsbad, Mission Valley and Parkway Plaza, as well as Irvine, said it is cooperating with health agencies to help determine the bacteria source.
Possible sources include lettuce and beef.
The chain said it has removed from its menu all products that might be suspected of contamination. Investigators also are focusing on food suppliers.
HHSA urges anyone looking for more information on E. coli to visit the Centers for Disease Control and Prevention Web site, www.cdc.gov.