The Centers for Disease Control and Prevention is once again investigating an outbreak of E.Coli that has been linked to Chipotle restaurants in three states that were not included in the outbreak that sickened dozens of diners in October.

The CDC reports five new cases: three in Oklahoma, one in Kansas and another in North Dakota. The affected individuals reported their symptoms began on dates between Nov. 18 and Nov. 26, and all of them reported eating at Chipotle in the week before the illness started.

The new cases have a different DNA fingerprint than the STEC 026 E.Coli strain linked to Chipotle across nine states in October, with the most recent case involving an individual who became sick on Nov. 10. Due to this, investigators are unsure if the newest outbreak is related to the previous one and have left the illnesses out of the first case's count.

In the meantime, Chipotle is working with the CDC, Federal Drug Administration and state health officials to investigate the newest outbreak, reported CNN. The investigation has yet to determine a single food item that is responsible for the illnesses.

"We have indicated before that we expected that we may see additional cases stemming from this, and CDC is now reporting some additional cases. Since this issue began, we have completed a comprehensive reassessment of our food safety programs with an eye to finding best practices for each of the ingredients we use. We are now in the process of implementing those programs...," said Chipotle Communications Director Chris Arnold.

Beyond the two E.Coli outbreaks, Chipotle has had to deal with two other outbreaks in recent months. Earlier this month, a location in Boston was shuttered by health officials after an outbreak of norovirus caused at least 140 cases of acute gastroenteritis, reported USA Today, while in September, a Minnesota location learned that its tomatoes were the cause of an outbreak of salmonella that sickened at least 64 people.

The chain's shares have taken a beating since news of the various outbreaks hit. Once standing as one of the most coveted stocks over the last three years, the stock was down 30 percent in Monday trading from its high of $757.77 in August.