Chipotle said when the Salmonella Newport outbreak was first detected last week that it switched produce suppliers for its Minnesota restaurants. However, officials are still trying to confirm which farm the tomatoes came from.
A total of 64 people have been infected.
The investigation identified 22 different Chipotle restaurant locations and people were likely infected between August 16 and August 28. Those infected are between 10 and 69 years old, with nine people hospitalized.
State testing protocols help health officials identify such outbreaks. Officials are alerted whenever two or more positive hits on the same strain of a bacteria occur within a short time frame.
The Minnesota health agency noted that many cases of salmonella go unreported, and urged anyone who suspects they are infected to get tested.
Among the symptoms of salmonellosis are diarrhea, abdominal pain and fever. In extreme cases the infection can result in blood stream infections, meningitis or even death in those with weakened immune systems.