The E. coli outbreak recently linked to Chipotle has spread to Illinois, Maryland, and Pennsylvania, bringing the total number of US states affected to nine, according to a new report from the Centers for Disease Control and Prevention (CDC). California, Minnesota, New York, Ohio, Oregon, and Washington have also reported cases in the past two months.

"The CDC is investigating"

Of the 52 total current reported cases, 47 reported eating at Chipotle before getting sick, according to the CDC. Of the three most recent illnesses (all reported in November), only one person had eaten at Chipotle. The current available information includes cases reported between October 19th and November 13th. If a person became sick after that time period, the case may not have been documented yet, because the reporting process takes an average of two to three weeks.

Chipotle has tightened its food safety measures in response. Today, the company announced it would implement high-quality testing for all produce before shipping to restaurants, The Wall Street Journal reports. It also said it would improve employee training for food handling. Chipotle spokesman Chris Arnold told WSJ the chain may have to rely less on local produce in the future, because smaller farms may not be able to meet its newly enhanced standards.

Washington has reported the highest number of E. coli cases so far (27) while Oregon has reported 13. The remaining states have reported three or fewer instances of illness, according to the CDC. As of December 2nd, there have been 20 hospitalizations and no deaths as a result of the outbreak. The CDC is investigating the source of the outbreak, which is still unknown as this time.