The CDC announced this week it is investigating a new batch of E. coli illnesses reported in November linked to Chipotle—though it is not known if these infections are related to the larger outbreak that has affected more than 50 people across nine states

The centers say five additional people—one from Kansas, one from North Dakota and three from Oklahoma—have tested positive for a rare DNA fingerprint of Shiga toxin-producing E. coli 026 (STOC 026). All five of these individuals reported eating at a Chipotle Mexican Grill restaurant in the week before the illness started. CDC reported the North Dakotan had traveled to Kansas during the exposure period and ate at the same Chipotle location as the person from Kansas who fell ill. These illnesses started on dates ranging from Nov. 18 to Nov. 26.

To determine if these recent infections are genetically related to the larger outbreak, investigators are using whole genome sequencing. To date, no exact ingredient has been identified as the source of the E. coli bacteria though 46 of the 52 people interviewed by investigators who were part of the larger outbreak reported eating at a Chipotle restaurant in the week before becoming ill.

Since the outbreak, Chipotle has pledged to become a leader in food safety, committing to deep cleans of its restaurants and implementing new training and food safety policies. But as news of the outbreak spread across the country, Chipotle’s sales have taken a hit.

In a recent regulatory filing, Chipotle detailed just how much the outbreak has affected business with sales dropping by as much as 22 percent in the weeks following the announcement of the outbreak. Should these trends continue, the company says it thinks sales for the final three months of the year could be down 8 to 11 percent. Because of this, Chipotle says it can no longer reasonably estimate sales for 2016.