Federal health officials have dramatically reversed an earlier conclusion about the source of a nationwide parasite outbreak that has sickened at least 1,600 people, acknowledging that a key piece of evidence linking the illnesses to a major lettuce supplier was incorrect.

On Shabbos, the Food and Drug Administration announced that it had traced the cyclospora outbreak to contaminated iceberg lettuce supplied by Taylor Farms, a company that provides produce to Taco Bell. Just one day later, however, the agency withdrew that finding after determining its original analysis had produced a false positive.

The FDA said it reexamined the testing results and concluded that Taylor Farms’ iceberg lettuce should not have been identified as the source of the contamination.

Taylor Farms confirmed that the FDA had apologized for the mistake. In a statement, the company said its “thoughts remain with everyone who has fallen ill” in the outbreak.

Although no fatalities have been reported, the outbreak has led to nearly 100 hospitalizations and has infected at least 1,600 people nationwide. The Centers for Disease Control and Prevention has classified the incident as a major outbreak.

Cyclospora infections often do not become apparent immediately, with symptoms sometimes taking up to two weeks to develop. Those infected can experience severe bouts of sudden, watery diarrhea that may continue for several days, along with a sharp loss of appetite and significant weight loss.