Sheetz convenience store workers are not to blame for 34 cases of salmonellosis in 11 Pennsylvania counties according to health officials interviewed by CS News and the Associated Press.

The salmonella bacteria is believed to have been on tomatoes and lettuce served on deli sandwiches made at 16 Sheetz stores in the Pittsburgh area and along the Pennsylvania Turnpike but the food was likely contaminated when it came from a supplier — which hasn’t been identified.

Altoona, Pennsylvania-based Sheetz operates more than 300 stores in Pennsylvania, Ohio, Maryland, West Virginia, Virginia and North Carolina. The company has changed its tomato supplier and pulled tomatoes and lettuce from its stores before disinfecting them and re-supplying them. The stores do not sell the produce separately.