Health officials initially traced 34 case of salmonella poisoning throughout western Pennsylvania to Sheetz stores, which has pulled the lettuce and Roma tomatoes suspected of causing the illness.
The Altoona-based chain also switched produce suppliers and disinfected its sandwich counters at more than 300 stores in Pennsylvania, Ohio, Maryland, West Virginia, Virginia and North Carolina.
Coronet Foods, of Wheeling, W.Va., which supplies produce to Sheetz, said it stopped buying and processing Roma tomatoes pending its own investigation. The company also quarantined its remaining inventory, reorganized the tomato processing line and notified growers and suppliers.
In a statement, Coronet officials noted that sliced Roma tomatoes make up 1 percent of their line, and most of it is distributed to Sheetz.
The Pennsylvania Agriculture Department was testing food samples Thursday to confirm the presence and type of salmonella bacteria.
Salmonella bacteria can contaminate food or water, and those who infected by it generally suffer from diarrhea, fever and cramps for up to three days. It can be fatal in rare cases.
Health officials said Thursday there were more than 60 confirmed cases -- 50 in 12 Pennsylvania counties. In Maryland, public health officials confirmed at least 14 cases; West Virginia had one confirmed case.
Ohio health officials were unaware of any cases linked to the convenience stores. But the federal Centers for Disease Control and Prevention said there were an unspecified number of cases in Ohio involving people who ate at Sheetz stores.
Sheetz officials did not immediately return calls Thursday.