The U.S. Food and Drug Administration said Sunday that a sample of shredded iceberg lettuce from Taylor Farms de Mexico previously reported to have tested positive for Cyclospora was actually a false positive, walking back a key finding in an ongoing nationwide investigation into a foodborne illness outbreak that has sickened more than 1,600 people across five states.

The FDA said the false positive result was discovered after the agency re-reviewed test data collected from a Taylor Farms de Mexico sample, and that the correction does not affect the company's earlier voluntary recall of iceberg lettuce sourced from central Mexico, which remains in effect. In its original Saturday notice announcing the positive test, the agency had said the affected product was not part of Taylor Farms' existing recall and that the company was working to determine whether any of that specific lot remained in commerce or in consumers' homes. That notice has since been removed from the FDA's public updates on the outbreak.

What caused the false positive

According to the FDA, Saturday's erroneous result stemmed from what the agency described as false amplification during laboratory testing. "The finding does not represent true amplification and should be considered a false positive," the agency said. Amplification techniques are commonly used in clinical laboratories to generate additional copies of biological samples, making pathogens easier to detect and identify, but the process can occasionally produce misleading results requiring further verification.

With Sunday's correction, FDA officials said there are currently no confirmed positive product samples tied to the outbreak, even as the underlying........

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