An outbreak of food poisoning that sickened dozens of people who ate at Chipotle restaurants in Minnesota last month has been traced to tomatoes used by the chain.

More cases of salmonella Newport infections have been reported since the outbreak was announced last week, according to the Minnesota Department of Health. The 64 cases at 22 Chipotle locations — including 19 stores across the metro — have resulted in nine people being hospitalized, with all expected to recover.

“We expected to see additional cases because it can take up to 10 days for salmonella to appear [and] another few days to a week before people go to their doctors and the cases get reported to us,” said state epidemiologist Dana Eikmeier.

At least two lawsuits have been filed due to the outbreak, one by a Rosemount man who became sickened Aug. 28 after eating at Chipotle three times in the previous two weeks and another by a Minneapolis woman who ate at Chipotle on Aug. 10 and suffered dehydration, blood clots and other symptoms that resulted in a weeklong hospital stay.

Infections were traced to meals served from Aug. 16 to 28. Locations included restaurants in Minneapolis, St. Paul and suburbs across the metro, as well as in Mankato, Rochester and St. Cloud. The Health Department is working with investigators to try to determine where the tomatoes were grown and distributed. Officials said there is no ongoing health threat; Chipotle has switched tomato suppliers and the tainted product was removed from store shelves.