Taco Bell Corp. learned Monday that green onions were not the source of an E. coli outbreak that has sickened dozens of customers at its East Coast restaurants. But health officials reported that white onions at one of its New York restaurants were tainted by a different E. coli strain.
The disclosures reflect the difficulties faced by company officials and federal health investigators in their quest to pinpoint the source of the illness. Last week, Irvine-based Taco Bell banished green onions from its 5,800 restaurants after a preliminary test pointed to the produce as the likely culprit behind the illness of 64 people from five states.
On Monday, the U.S. Food and Drug Administration said it was unable to confirm the preliminary result and was now looking at a range of foods besides green onions as possible sources.
Absent a culprit, the FDA will test tomatoes, lettuce, cilantro, white onions and cheese, foods that based on other outbreaks could be E. coli sources, said Dr. David Acheson, chief medical officer at the agency's Center for Food Safety and Applied Nutrition in College Park, Md.
"But we can switch away from green onions now. They aren't implicated," he said.
The green onions that were suspected in the outbreak were grown by Boskovich Farms Inc. of Oxnard and processed at a New Jersey plant owned by Irwindale-based Ready Pac Produce, according to those companies. Taco Bell never identified the source of the green onions.
Other than acknowledging that the new tests were negative, Boskovich Farms didn't comment on the positive news about its green onions. The company issued a statement saying "the safety of consumers is our top priority." It pledged "continued cooperation with all agencies as they try to determine the cause of this tragic situation."
Concern over the safety of Taco Bell's food has led to investigations by state and federal regulators. In Nassau County on New York's Long Island, health inspectors tested Taco Bell ingredients and discovered a different strain of E. coli in a batch of chopped white onions at one restaurant, according to Acheson. Health officials haven't linked any illnesses to this strain.
Genetic fingerprinting ruled out the pathogen in the white onions as the source of the current outbreak and health officials have not linked it to any other illnesses, he said.
The FDA has not determined where those onions were grown or the contamination's source.
"Obviously it is a concern that it was found and raises the possibility that people could become sick," Acheson said.
Taco Bell said Monday that a private laboratory it hired, Certified Laboratories in Plainview, N.Y., tested 300 food samples from its restaurants in the Northeast and found no evidence of E. coli.
"Based on this testing and all that we know today, I can reassure you that all Taco Bell food is safe and strict standards are being upheld at all of our restaurants," Greg Creed, president of Taco Bell Corp., said in a statement.
Creed said Taco Bell switched its produce supplier in the region from Ready Pac to Taylor Farms of Salinas "as a precautionary measure."
The Centers for Disease Control in Atlanta said it had not seen any new cases of people stricken with the disease in several days, raising the possibility that the outbreak had ended.
"We will monitor this situation for another day or two to see if it is over," said Dr. Christopher Braden, a CDC epidemiologist.
In addition to the confirmed cases, the CDC suspects an additional 22 people may have been sickened by E. coli, said Braden. Several hundred more people claim to have become ill after eating at a Taco Bell, but their link to the outbreak has not been confirmed, he said.
Braden said health officials also were looking into a suspected E. coli outbreak that may have affected as many as 30 people at an eastern Iowa outlet of Taco John's, a fast-food chain based in Cheyenne, Wyo.
The CDC wants to know whether that strain matches the pathogen found in the Taco Bell cases.
Shares of Louisville, Ky.-based Yum Brands Inc., which owns Taco Bell, KFC and Pizza Hut, fell 22 cents to close at $59.50 before the FDA news conference about the E. coli tests.