(CNBC) — Shares of Chipotle Mexican Grill hit a 52-week low Monday after the Centers for Disease Control and Prevention (CDC) announced it is investigating another, more recent outbreak of a different strain of E. coli linked to the restaurant chain.
The CDC does not know yet if they are linked to a larger outbreak that began at the end of October.
Five ill people were identified in Kansas, North Dakota and Oklahoma as part of the new investigation, on dates ranging from Nov.18 to Nov. 26, 2015. Illnesses associated with the new investigation are not being linked to the current case count, which is now at 53, the CDC report said.
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