The U.S. is curbing shellfish imports from South Korea after food safety regulators determined that inadequate sanitation may have exposed oysters, mussels, clams and scallops to human fecal waste.

The Food and Drug Administration removed Korean shippers from its certified shellfish list on May 1, Curtis Allen, an agency spokesman, said in an e-mail today. The FDA cited risks from water and land-based pollution, and said any imports from the nation prior to this month shouldn’t be sold or consumed.

The contamination may lead the shellfish to carry the norovirus, which isn’t typically life-threatening and can cause nausea, vomiting, diarrhea and stomach cramping. No illnesses from the consumption of Korean shellfish have been reported this year, Allen said. Korean shellfish represents a small amount of the shellfish sold in the U.S., he said.

“Korean molluscan shellfish that entered the U.S. prior to May 1 and any product made with Korean molluscan shellfish are considered adulterated,” Allen said. Removal of Korean shippers from the certified list “is intended to stop the import of molluscan shellfish harvested from polluted waters.”

The FDA is working to determine where the product has been distributed. (Bloomberg)