WASHINGTON -- Several outbreaks of ciguatera fish poisoning have been confirmed in consumers who ate fish harvested in the northern Gulf of Mexico, the Food and Drug Administration said Tuesday.

The FDA said that fish such as grouper, snapper, amberjack and barracuda represent the most significant threat to consumers. They feed on fish that have eaten toxic marine algae. The toxin is stable in the tissue of living fish and does them no harm. But larger carnivores have higher concentrations of the toxin in their tissues. As a result, the greatest risk of poisoning for humans comes from the largest fish.

Symptoms of ciguatera poisoning include nausea, vomiting, vertigo and joint pain. In the most serious cases, neurological problems can last for months or even years. Several outbreaks of the illness were confirmed in Washington, D.C., and St. Louis, the FDA said, without citing an exact number.

The fish linked to the illnesses were harvested near the Flower Garden Banks National Marine Sanctuary, an area of 56 square miles in the northwestern Gulf. The FDA recommends that processors not purchase fish harvested near the sanctuary.

Ciguatera is common in fish living in tropical and subtropical regions, including the Caribbean Sea, the South Pacific Ocean and the Indian Ocean. But the FDA has considered it rare for fish in the northern Gulf of Mexico to have the toxin.

The FDA warned processors to reassess their hazard control plans as necessary, and that failure to take proper precautions may cause products to be considered adulterated by the agency.

Consumers who think they may have ciguatera poisoning are encouraged to report their symptoms and what fish they ate to a doctor or local health department.