The CDC announced on Monday that Chipotle Mexican Grill's E. coli outbreak is over.
Two separate outbreaks of the bacteria were investigated by the U.S. Food and Drug Administration, the U.S. Department of Agriculture's Food Safety and Inspection Service and public health officials in several states.
In the first outbreak 55 people were infected by the foodborne illness in 11 states, of which 21 were hospitalized. The second, smaller outbreak, infected five people from three states, of which one was hospitalized.
The CDC determined that 57 percent of people affected by the first outbreak and 80 percent of people affected by the second outbreak were female.
There were no reports of hemolytic uremic syndrome, which can lead to kidney failure, and no deaths in either outbreak.
Chipotle stock was up 4 percent on the news.
"We are pleased that the CDC has concluded its investigation, and we have offered our full cooperation throughout," Chris Arnold, a spokesman for Chipotle, said in a statement. "Over the past few months we have taken significant steps to improve the safety of all of the food we serve, and we are confident that the changes we have made mean that every item on our menu is delicious and safe."
Investigators were not able to identify the ingredient that was responsible for the contamination.