A study of the salmonella outbreak that sickened more than 250 customers at Sheetz convenience stores suggests that Roma tomatoes were the source of the infection, the state Department of Health said yesterday in a Pittsburg Post-Gazette interview with Christopher Snowbeck.

The state compared the food histories of about 50 people who ate at Sheetz and didn’t get sick, with the histories of another 50 or so who became ill. Investigators found a strong link between tomatoes and sickness.

The customers who became ill ate many different kinds of sandwiches and salads, but almost all of them reported eating tomatoes to the Department of Health.

With those results in hand, the U.S. Food and Drug Administration said yesterday its investigation of a regional salmonella outbreak was focusing on certain pre-sliced Roma tomatoes sold at deli counters in Sheetz stores between July 2 and 9.