SAN FRANCISCO (CBS SF) — Officials with the California Department of Public Health (CDPH) issued a warning on Wednesday advising consumers against eating mussels, clams or whole scallops sport-harvested by from San Francisco and San Mateo counties due to dangerous levels of toxins.

The advisory stated that sport-harvested bivalve shellfish in those two counties were testing for dangerous levels of paralytic shellfish poisoning (PSP) toxins. The naturally occurring PSP toxins can cause illness or death in humans. Cooking does not destroy the toxin.

The Department of Public Health wants to be clear that the shellfish toxin warning does not apply to commercially sold clams, mussels, scallops or oysters from approved vendors. State law permits only state-certified commercial shellfish harvesters or dealers to sell these types of shellfish. The products sold by certified harvesters and dealers are subject to frequent mandatory testing to monitor for toxins.

PSP toxins affect the central nervous system, producing a tingling around the mouth and fingertips within a few minutes to a few hours after eating toxic shellfish. These symptoms are typically followed by loss of balance, lack of muscular coordination, slurred speech and difficulty swallowing. In severe poisonings, complete muscular paralysis and death from asphyxiation can occur.

Consumers can get the most current information on shellfish advisories and quarantines by calling CDPH’s toll-free Shellfish Information Line at 1-800-553-4133. For additional information, please visit the CDPH Marine Biotoxin Monitoring Web page.