The U.S. Food and Drug Administration said on Monday that its traceback investigation into a cyclosporiasis outbreak across five states continues to support Taylor Farms’ lettuce from Central Mexico as a product source.

In a post on X, it said it was confident that shredded iceberg lettuce from Taylor Farms locations in central Mexico is behind illnesses associated with Yum Brands’ Taco Bell restaurants in Michigan and four other states.

On Saturday, the FDA had said a lettuce sample from border surveillance of product from Taylor Farms de Mexico tested positive for the cyclospora parasite. But on Sunday, it said that should be considered a false positive following a re-review by laboratory experts.

Cyclosporiasis is an intestinal infection that can be contracted by consuming food, typically raw fruits and vegetables, or water contaminated with feces, according to the U.S. Centers for Disease Control and Prevention.

Gottlieb Says Investigation Matters More

Former FDA Commissioner Scott Gottlieb said on Monday that the false-positive result did not undermine the agency’s conclusions because investigators were relying primarily on epidemiological evidence rather than laboratory testing.

“The particular test that tested positive that turned out to be a false positive was on recent samples. And so this isn’t the product that was affected – it went into the supply chain three weeks ago,” Gottlieb said.

Michigan health officials reported 6,148 cases linked to the outbreak on Monday, an increase of 1,146 cases since their last update on Friday. The outbreak has resulted in 102 hospitalizations in the state, with no deaths reported.

Consumer foot traffic fell 18.9% at Taco Bell on Friday, compared with the day-of-week average between January 1 and July 6. Traffic at restaurant chains Chipotle and Cava was down 6.9% and 4.2%, respectively, on the same day, according to data by Placer.ai.

“The cyclosporiasis outbreak is affecting how consumers view Taco Bell in the short term – and will likely hurt sales and traffic this quarter – but is unlikely to lead to a long-term decline in revenues or perception,” said Rachel Wolff, analyst at eMarketer.

(Reporting by Siddhi Mahatole and Neil J Kanatt in Bengaluru, Yasmeen Abutaleb in Washington; Editing by Maju Samuel and Pooja Desai)