Castellini Co., of Kentucky, and three California firms -- Newstar Fresh Foods, LLC; Apio Fresh, LLC; and Boskovich Farms, Inc. -- are named in the suit, which was filed in federal court in Pittsburgh.
The Marler Clark law firm filed the suit on behalf of Richard Miller, a liver transplant patient, and Miller's wife, Linda. Like many of the 615 confirmed hepatitis patients, the Millers say they ate at the Beaver Valley Mall Chi-Chi's restaurant in October.
Richard Miller's medical bills as a result of his infection and transplant have exceeded $500,000 so far, according to the lawsuit.
Marler Clark said its own investigation identified the companies in the lawsuit, and it said Chi-Chi's confirmed the names.
A statement released Monday afternoon by Chi-Chi's said attorney William Marler had decided to dismiss lawsuits against the restaurant and sue the alleged onion suppliers instead.
Meanwhile, investigators with the Food and Drug Administration are visiting onion exporters in Mexico to see if conditions are up to U.S. standards. The Mexican government has shut down four export companies so far.