Chipotle co-CEO Steve Ells said that half of the burrito chain's more than 2,100 restaurants have less-than-excellent customer service and that the company is now training employees.
The number of Boston College students who became ill after eating at a Chipotle restaurant near its campus grew to 80 on Tuesday.
Sales and stock at Chipotle took a hit after the outbreaks.
The Chipotle chain voluntarily shut down 43 restaurants in Washington state and Oregon over the weekend after health authorities began investigating an E. coli outbreak.
Chipotle projected fourth-quarter earnings of $2.45-$2.85 per share, much below the $4 expected by analysts.
The latest crisis began last month when Chipotle closed 43 restaurants in Washington state and Oregon after health authorities linked an E. coli outbreak to six restaurants in the region.
Chipotles same-store sales dropped by 14.6 percent in the last quarter.
In the aftermath of an E. coli outbreak at Chipotle, restaurants that once sported long lines were suddenly empty, a phenomenon that was almost surely happening nationwide.
In a first for a major restaurant chain, Chipotle Mexican Grill on Monday will begin serving only food that is free of genetically engineered ingredients.
British politicians have a lot to learn from Hillary Clintons flawless trip to Chipotle for a chicken burrito bowl.