The Illinois Department of Health is investigating a salmonella outbreak that has resulted in almost 100 confirmed cases of illness in people who ate at Subway sandwich restaurants in the state.
Investigators confirmed 97 cases of Salmonella Hvittingfoss infection from 28 Illinois counties as of Monday, spokeswoman Kelly Jakubek told Reuters.
The uncommon strain of Salmonella, which sent 26 people to hospitals, but caused no deaths, has been linked to 47 Subway restaurants in central Illinois, she said.
The attacks of Salmonella poisoning took place between May 11 and June 5, Jakubek said.
The source of infection has not yet been identified and Subway, one of the largest U.S. restaurant chains, voluntarily withdrew some items including onions, green peppers, tomatoes and lettuce from its restaurants in early June as a precaution.
Subway did not return calls for comment.
Poultry, leafy green vegetables and nuts and fruits were the chief vehicles of foodborne illness in 2006 U.S. officials said.
Privately held Subway is owned by Doctor's Associates Inc and has more than 28,500 locations in 86 countries.