FDA Deputy Commissioner Lester Crawford said the U.S. Centers for Disease Control on Friday will release an update on the outbreak, including the food source that has caused at least three deaths and where it originated.
Health officials believe Mexican green onions served at a Chi-Chi's restaurant were the source of the Pennsylvania outbreak. Recent cases of the liver disease in Tennessee, North Carolina and Georgia have also been linked to scallions.
"We are actually detaining the (green onions) at the border at the present time," Crawford said after testifying on an unrelated issue at the House Governmental Affairs committee. "This is the best bet of the source, but has not yet been finally confirmed."
Crawford said there were no indications the hepatitis A outbreak was intentional.
Hepatitis A is usually mild but can cause fever, exhaustion, vomiting, abdominal pain and in rare cases death.
As of Tuesday, 520 cases of the illness had been confirmed in Pennsylvania, the state health department said on its Web site.
The Chi-Chi's Mexican restaurant chain voluntarily pulled green onions off the menu at all its more than 100 restaurants after employees and patrons of Beaver Valley, Pennsylvania, restaurant became ill from hepatitis A.
The chain is owned by Irvine, California-based Prandium Inc..