A food safety investigation involving shredded iceberg lettuce has ended without a definitive answer about exactly how the produce became contaminated.
Mexico's Health Ministry said the US Food and Drug Administration investigation failed to conclusively identify the source of contamination linked to a Cyclospora outbreak.
Reuters reports that the investigation focused on lettuce produced by Taylor Farms in Mexico.
Cyclospora is a microscopic parasite capable of causing an intestinal illness known as cyclosporiasis. Symptoms can include diarrhea, stomach cramps, fatigue and loss of appetite.
Foodborne outbreaks involving fresh produce can be particularly difficult to trace because vegetables often pass through farms, processing facilities, distributors and retailers before reaching consumers.
By the time illnesses are detected, contaminated products may already have been consumed or removed from shelves.
The inconclusive investigation highlights the difficulties health authorities face when trying to reconstruct contamination events across international food supply chains.
Officials continue to emphasize surveillance and food safety controls as the most important tools for identifying outbreaks quickly and limiting their spread.
