WASHINGTON >> The Food and Drug Administration is urging food distributors, retailers and food service vendors to remove from the market oysters, clams, mussels and scallops imported from South Korea because of possible contamination with human waste and norovirus.

The decision follows an FDA evaluation that determined that the Korean Shellfish Sanitation program no longer meets adequate sanitation controls. The federal agency is in discussions with South Korean authorities to resolve the issue.

The sanitation program’s deficiencies caused the FDA to remove five South Korean firms that shuck and pack shellfish from the Interstate Certified Shellfish Shippers List on May 1. The warning covers all fresh, frozen canned or processed mollusks from South Korea. Some contaminated fish may have entered the U.S. before May 1. International shippers on the list are included under the terms of the shellfish sanitation agreements between the FDA and the countries of origin.

An FDA spokesman, Curtis Allen, said Thursday the decision to call for the removal of the mollusks from the market was precautionary and began with an investigation into norovirus outbreaks in November and December.

“We want to ensure that all foods coming into the United States are safe for consumption,” Allen said Thursday.

Curtis said no illnesses from eating the shellfish have been reported this year. Four norovirus illnesses, including three in Washington state, were reported in 2011. Norovirus causes vomiting or diarrhea.

In a statement released Thursday the FDA said that no other shellfish shippers on the certified list were affected. Mollusks harvested in non-Korean waters are not affected either.

Concerned consumers are being advised to check the package label for country of origin or to contact the store where the shellfish was purchased or the manufacturer. The FDA recommends consumers dispose of mulluscan shellfish from Korea or any products made from them.