The FDA says it still hasn’t determined how tomatoes were tainted with salmonella before they sickened at least 429 convenience store customers in Pennsylvania, Maryland, West Virginia and Ohio.

In August, WBAL reports, Hurricane Charley wiped out some evidence when it struck Florida farms where the tomatoes were grown. Officials believe the tomatoes were likely tainted by animals that came into contact with the fruits at the farm level or in storage sheds.

Customers became ill after eating sandwiches from Sheetz convenience stores this past summer.

Bad publicity from the outbreak put a West Virginia produce supplier, Coronet Foods, out of business.