The FDA says it is investigating a third outbreak of E. coli O157:H7 illnesses that matches the strain found by Michigan authorities in Tanimura & Antle brand packaged single head romaine lettuce.

In late October the administration announced there were two active E. coli outbreaks with genetic links to past romaine events.

Then this week, Tanimura & Antle announced that it was recalling 3,396 cartons of potentially affected product that were distributed to 20 states.

At this time, there is not enough epidemiologic and traceback evidence to determine if ill people in this outbreak were exposed to romaine lettuce from Tanimura & Antle.

"It is important to note that the E.coli strain identified in this outbreak is not genetically related to either of the E. coli strains that we reported investigating on Oct. 28. This is a new and separate outbreak," said Frank Yiannas, FDA Deputy Commissioner for Food Policy and Response.

"At this time, there is not enough epidemiologic and traceback evidence to determine if ill people in this outbreak were exposed to romaine lettuce from Tanimura & Antle, Inc. Additional information will be provided as it becomes available.

"Consumers, restaurants and retailers should not eat, sell or serve recalled Tanimura & Antle, Inc. brand packaged single head romaine lettuce with a pack date of Oct. 15 or 16. We are actively investigating with our partners and will provide additional information as it becomes available.

He said the investigation reinforces the recommendations to the leafy greens industry that producers should continue to review their practices and reinforces that traceability can assist with investigations.

It remains unknown if the first two E. coli outbreaks announced on Oct. 28 are linked to romaine lettuce.

The announcement of a third investigation comes as a major blow to the U.S. leafy green industry, which has been implementing stringent food safety protocols following numerous outbreaks linked to leafy greens over the past few years.

In 2019, an E. coli outbreak tied to romaine lettuce spread to at least 23 states in November, leading the Centers for Disease Control and Prevention (CDC) to specifically warn families against serving lettuce on Thanksgiving. 

And in early October this year, Canada announced it was implementing tighter restrictions on romaine lettuce imports from the U.S.