An Illinois division of Houston-based Sysco Corp. likely distributed the food linked to a salmonella outbreak at Subway restaurants earlier this year, and produce was the likely culprit.

While it remains uncertain exactly how consumers became ill, signs point to Lincoln, Ill.-based Sysco Central Illinois Inc. as the distributor, just as they earlier pointed to Subway as the restaurant, Melaney Arnold, a spokeswoman for the Illinois Department of Public Health, said Oct. 27.

“There were some common denominators,” Arnold said. The people ate at Subway, and in all but three of the restaurants involved, the distributor was Sysco, she said.

An Oct. 14 summary of the outbreak from the Centers for Disease Control and Prevention concluded Sysco was the link.

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Another was that the outbreak was “statistically linked” to lettuce, tomatoes and olives, which means that at least one-third of those infected ate one or more of those items, according to the CDC report.

Sysco had no role in processing or repacking the produce, so contamination in a Sysco facility was near impossible, said Mark Palmer, vice president of corporate communications for Sysco’s corporate office. The lettuce and olives were pre-cut and bagged, and the tomatoes were boxed but supplied to the restaurants whole in their original packing.

“This was not Sysco produce,” Palmer said. “It was produce that was bagged that we did not process at all. It’s important that people understand what our role is as a distributor, not the source of the food.”

Palmer said the company cooperated fully with investigations by the state department of health and the Food and Drug Administration, neither of which turned up any positive tests for salmonella.

After the outbreak, federal, state and local investigators cited fresh produce as a “possible” source of the salmonella outbreak, which sickened 97 customers and 12 Subway workers in 28 counties. The first illness was reported April 25, the last June 30, according to the report.

After diners began reporting illnesses last spring, Subway replaced lettuce, green peppers, red onions and tomatoes in restaurants.

Markets Editor Andy Nelson contributed to this article.