FDA investigators found Cyclospora at Taylor Farms' lettuce processing facility in Central Mexico and on a contract grower's farm, the agency announced Oct. 2, confirming the supply link behind an outbreak that sickened 12,883 people this summer.

The CDC counted 570 hospitalizations and two deaths before declaring the outbreak over on Sept. 11. The scale makes it one of the largest Cyclospora outbreaks on record, and the source sits squarely in the restaurant supply chain: iceberg lettuce distributed by Taylor Fresh Foods and used in menu items at Taco Bell, where early cases among patrons first surfaced in July.

The FDA's traceback investigation identified several farms and a processing facility in Mexico that supplied lettuce later recalled by Taylor Fresh Foods. Working with Mexican officials, agency investigators conducted onsite inspections and collected samples across multiple iceberg lettuce growers and the processing facility.

Sampling covered water, soil, sediment and iceberg lettuce. Two samples tested positive for Cyclospora. The first came from a tank holding outgoing wastewater at the Taylor Farms de Mexico processing facility. The second came from a drainage ditch at an iceberg lettuce grower identified in the traceback.

Genotyping of both positive samples is complete, but the FDA is still analyzing how those results relate to ongoing genotyping of specimens from outbreak patients.

The agency says it does not yet have enough evidence to conclusively determine how contamination occurred. Even so, the positive samples demonstrate that Cyclospora was present in the environment where the lettuce was grown and processed. That evidence adds to what the FDA describes as strong epidemiological data and traceback convergence linking the outbreak to recalled shredded iceberg lettuce from the Taylor Farms operation in Central Mexico.

For operators, the findings harden the connection between a single produce supplier and more than 12,000 illnesses across dozens of states, a reminder of how concentrated fresh-cut lettuce sourcing concentrates risk. Taylor Farms supplies leafy greens to major quick-service chains nationwide, and a facility-level contamination event at that scale reaches menus across multiple brands simultaneously.

A Taylor Fresh Foods spokesperson told ABC News that the Central Mexico facility remains closed while the company's research team develops enhanced safety protocols. The independent grower where the second positive sample was found is no longer part of the company's supplier program.

The FDA's ongoing genotyping analysis of patient specimens against the environmental samples is the next step that could establish precisely how contamination entered the supply — and what the reopened facility's protocols will need to address before production resumes.