ATLANTA, Dec. 4 (UPI) -- The Centers for Disease Control and Prevention on Friday expanded a recent outbreak of E. coli, that was linked to the Chipotle restaurant chain, to include three additional states.
The states that had reported E. coli illnesses are Washington (27), Oregon (13), California (3), Minnesota (2), New York (1) and Ohio (3). Friday's update added seven more individual cases and Illinois (1), Maryland (1), and Pennsylvania (1) to the list.
In all, the CDC said, 52 people have reported being sickened by the Escherichia coli O26 strain.
The outbreak was previously said to be linked to the Chipotle Mexican restaurant chain but investigators have yet to find the source. Chipotle closed several locations upon learning of the E. coli outbreak but later reopened when officials couldn't determine a source.
Despite the failure to track down the source of E. coli, the CDC said it believes the spread originated with the restaurant chain.
"The epidemiologic evidence available at this time suggests that a common meal item or ingredient served at Chipotle Mexican Grill restaurants in several states is a likely source of this outbreak," the agency said in a news update.
Of the 52 people sickened, officials said 20 were hospitalized. The reported cases occurred between Oct. 19 and Nov. 13, officials said, and 90 percent (47) of those afflicted told investigators that they had eaten at a Chipotle location.
Of the three new cases, one told officials they had eaten at a Chipotle. Investigators said there still may be more cases, as well, since it takes a couple weeks for symptoms to begin.
The CDC said it is using advanced DNA sequencing to track down the source of the strain.
"This provides additional evidence that illnesses outside the Pacific Northwest are related to the illnesses in Oregon and Washington," the CDC said.