The FDA is backing away from its initial claim that a Taco Bell lettuce supplier was responsible for an outbreak that left hundreds of Americans suffering from explosive diarrhea, saying the agency’s original lab result was a “false positive.”

The reversal came after the FDA re-tested a lettuce sample and found the leafy greens supplied by Taylor Farms de Mexico did not contain Cyclospora, the parasite tied to the illness.

“FDA laboratory experts re-reviewed the sample results and have concluded that the finding does not represent true amplification and should be considered a false positive,” the agency said on its website Sunday.

The FDA also said there are currently no confirmed product samples that have tested positive for the parasite.

Taylor Farms, the parent company of Taylor Farms de Mexico, said the FDA acknowledged its error and apologized for the incorrect finding.

“Today, we were informed that FDA made a mistake, and this was a false positive,” Taylor Farms said in a statement.

The about-face overturns the FDA’s announcement Friday that connected the outbreak to Taylor Farms de Mexico, a subsidiary of Taylor Farms.

Federal officials had initially said contaminated lettuce was grown in central Mexico before being shipped to Taco Bell restaurants in Indiana, Kentucky, Michigan, Ohio, and West Virginia, where customers became ill.

Consumers were urged to throw away Taylor Farms iceberg lettuce, which is supplied to several fast-food chains in addition to Taco Bell and is also sold in grocery stores.

Taco Bell restaurants nationwide also stopped using the ingredient as a precaution.

Taylor Farms voluntarily recalled the lettuce and released a list of affected lot numbers distributed across 27 states.

Despite the revised test results, the FDA said it is continuing to work with the produce supplier to remove products believed to be connected to the outbreak from the marketplace while the investigation continues.

Cyclosporiasis, the illness caused by the microscopic Cyclospora parasite, has sickened more than 1,600 Americans across 34 states, according to the Centers for Disease Control and Prevention.

The disease is best known for causing prolonged diarrhea, along with symptoms including stomach cramps and low-grade fever, the CDC said.

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