DNA hunt on amid Chipotle-linked E. coli outbreak

Chipotle's industry-leading commitment to tracking its ingredients from farm to table is being put to the test by an E. coli outbreak that has sickened at least 37 people as of Tuesday, nearly all of whom ate recently at one of the chain's restaurants in Washington state or Oregon.

Scientists also said on Tuesday that they identified the specific microorganism responsible, which they believe was carried on fresh produce such as lettuce or tomatoes.

The chain of casual Mexican restaurants voluntarily closed 43 locations in the two states after health officials alerted them to a growing number of E. coli cases involving people who shared one common experience: a meal at Chipotle during the last two weeks.