The two most recent outbreaks linked to Chipotle Mexican Grill restaurants appear to be over, according to federal officials who say the root cause of the E. coli infections has not been determined. Testing of fresh produce, meat and other foods from Chipotle restaurants has not provided investigators with much insight, according to the Centers for Disease Control and Prevention. “Testing of multiple food items collected from Chipotle restaurant locations did not identify STEC O26 (E. coli),” the CDC reported today. “When a restaurant serves foods with several ingredients that are mixed or cooked together and then used in multiple menu items, it can be more difficult for epidemiologic studies to identity the specific ingredient that is contaminated.” Some sources have suggested beef from Australia as the source of the E. coli, but no such link has been found by the Food Safety Inspection Service (FSIS) of the U.S. Department of Agriculture. “As was stated by CDC earlier today, we’ve examined the evidence and have not been able to identify a source for these outbreaks,” an FSIS spokesperson said. “Distribution data shared by Chipotle does not establish a link between Australian beef, or any single source of beef, and the Chipotle restaurants where case patients reported consuming steak. Moreover, of the 60 case patients only eight reported consuming steak. “During this (investigation), Chipotle committed to several steps to improve sanitation practices and record-keeping in their supply chain and in their restaurants, including better record-keeping and improved employee training.” Chipotle’s stock was up more than 5 percent in early trading today as investors anticipated what the company’s executives have been saying for more than two weeks — that the two outbreaks that spanned 14 states and sickened 60 people are a thing of the past. The announcement from the Centers for Disease Control and Prevention today fits the Chipotle marketing campaign outlined by founder and co-CEO Steve Ells and other executives in mid-January. They told attendees at an investment conference the public would quickly forget about the outbreaks and that profits would be bigger than ever. Ells said media reports about the outbreaks had confused customers in recent months, but he said the new ad campaign launching in mid-February would not reference food safety problems or actions Chipotle took to avoid them in the future. The chain’s stock was trading at $754 in August 2015 and hit a low of $404 in January. Multiple financial and investment publications speculated during the last weekend of January that the public and mainstream media had already forgotten about the E. coli outbreaks, which were the fifth and sixth foodborne illness outbreaks for the restaurant chain in the second half of 2015. Hundreds of Chipotle’s customers were victims of those outbreaks:

Seattle — E. coli O157:H7, July 2015, five sick people, source unknown;

Simi Valley, Calif. — Norovirus, August 2015, 234 people, source was sick employee;

Minnesota — Salmonella Newport, August and September 2015, 64 sick people, source was tomatoes but it is not known at what point in the field-to-fork chain the pathogen was introduced;

Nine states — E. coli O26, began October 2015 and declared over Feb. 1, 55 sick people, source unknown, states involved are California, Delaware, Illinois, Kentucky, Maryland, Minnesota, New York, Ohio, Oregon, Pennsylvania and Washington;

Boston — Norovirus, December 2015, 151 sick people, source was sick employee; and

Three states — E. coli O26, began December 2015 declared over Feb. 1, five sick people, source unknown, states involved are Kansas, Oklahoma and Nebraska.

The FDA conducted tracebacks of multiple widely-distributed ingredients, according to an agency update posted late today. “No product of interest was identified. Even without a definitive item to follow, the FDA traced back to their origins some widely distributed ingredients in an effort to identify a source for the outbreak. Unfortunately, the distribution path did not lead to an ingredient of interest,” the agency reported. “The FDA also conducted investigations of some suppliers, but did not find any evidence that those suppliers were the source of the outbreak. Ultimately, no food item has been identified as causing the outbreak, and by the same token, no food has been ruled out as a cause.” (To sign up for a free subscription to Food Safety News, click here.)