(Reuters) - The U.S. Food and Drug Administration said on Tuesday it is investigating the more recent outbreak of a rare strain of E.coli linked to Chipotle Mexican Grill Inc.

Shares of the popular burrito chain operator fell as much as 5 percent to a 17-month low of $495.76 on Tuesday.

The FDA said it is working with the Centers for Disease Control and Prevention (CDC) and state and local officials.

The CDC said on Monday it was investigating five new cases of E.coli infections, one each Kansas and North Dakota and three in Oklahoma.

The two who fell ill in North Dakota and Kansas ate at the same restaurant in Kansas, while the three from Oklahoma ate at the same Chipotle restaurant, the FDA said. (http://1.usa.gov/1ZnMOCK)

Chipotle has been linked to a previous E.coli outbreak that has sickened 53 people in nine states with a different strain since late October.

The latest reports take the number of people sickened by E.coli outbreaks linked to Chipotle to 58 and the states affected to 12.

The FDA said on Tuesday the evidence available suggests that a common meal item or ingredient served at Chipotle's restaurants in several states is a likely source of both the outbreaks.

Chipotle's shares have fallen 22.6 percent since end October, when the first news of food poisoning was reported.

(Reporting by Yashaswini Swamynathan in Bengaluru; Editing by Sriraj Kalluvila)