The outbreak of an intestinal illness linked to McDonald’s salads has sickened 163 people in 10 states, with Illinois and Iowa residents representing the highest totals among them, the Centers for Disease Control and Prevention said late Thursday.

Three people have been hospitalized, according to the CDC, which is investigating the outbreak of cyclosporiasis in conjunction with the U.S. Food and Drug Administration and state health officials.

Cyclosporiasis is caused by the microscopic Cyclospora parasite and can cause diarrhea, stomach pain, fatigue and nausea among other symptoms.

It’s unclear exactly how many cases are confirmed in Illinois. As of July 13, there were 29 cases, according to data on the CDC website. As of Thursday, both Illinois and Iowa had a range of 21 to 70 cases.

Last week, the Illinois Department of Public Health reported 100 cases of the illness, but at the time only about one-fourth of the cases were linked to McDonald’s salads.

Chicago-based McDonald’s has said it has stopped selling the salads at 3,000 restaurants, of which at least one is located in the following 14 states: Illinois, Iowa, Indiana, Wisconsin, Michigan, Ohio, Minnesota, Nebraska, South Dakota, North Dakota, Montana, Kentucky, West Virginia and Missouri.

McDonald’s also said it was switching to another lettuce blend supplier.

The FDA and the CDC said they hadn’t identified which ingredient in the salads was the “vehicle for the outbreak.”

The agencies said there’s no evidence to link these illnesses with a separate cyclosporiasis outbreak linked to Del Monte vegetable trays.