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, said Richard McGarvey, spokesman for the Health Department.
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.
The FDA announced Tuesday that, as a precaution, it had begun a trace-back of those tomatoes in hopes of determining where contamination might have occurred. Health officials believe the tomato slices, which arrived in vacuum-sealed packages, were not contaminated at Sheetz.
Sheetz bought tomatoes from Coronet Foods of Wheeling, W.Va., and a Coronet Foods official has said that 99 percent of its pre-sliced Romas were sold to Sheetz. Earlier this week, state Department of Agriculture officials found a different sort of salmonella contamination on tomatoes distributed by Coronet to a Sheetz store in south central Pennsylvania.
The number of reported illnesses tied to the outbreak continued to increase yesterday.
In Pennsylvania, 210 cases are now linked to the outbreak.
Maryland, West Virginia and Ohio officials were reporting a combined 73 cases of salmonella among people who ate at a Sheetz. In Virginia, officials were looking at five cases that might be connected to the outbreak.
The newly reported cases refer to sicknesses from the first half of July -- not people coming down sick this week, said McGarvey. Most people ate food from Sheetz during the first 10 days or so of this month, but it now appears that some ate in late June, too, according to McGarvey.
Dr. Danae Bixler, an epidemiologist in West Virginia, said that her state is investigating four salmonella cases among people who didn't eat at Sheetz, but were sickened by the same bacteria strain. Pennsylvania officials have said it's possible establishments besides Sheetz served contaminated products from Coronet, but they have not made conclusive links.
Separately, the state Department of Agriculture announced that it is currently testing seven food samples for clues about the contamination source -- two more samples had been collected Thursday. Results aren't expected until Monday.