Health officials traced the cause of a nationwide explosive diarrhoea outbreak to iceberg lettuce supplied by Taylor Farms.

The U.S. Food and Drug Administration collected a sample the same week the outbreak was declared and confirmed the presence of Cyclospora, the parasite responsible for severe watery diarrhoea, rapid weight loss and loss of appetite.

Under voluntary action, Taylor Farms halted purchase of lettuce from the implicated Central Mexico lot and removed the product line from all U.S. retail outlets. The company is actively checking whether any of the affected batch remains in circulation.

CDC advice warns against eating shredded iceberg lettuce sold at Taco Bell restaurants in Indiana, Kentucky, Michigan, Ohio and West Virginia, where the recalled product had been sold. Taco Bell has said it has removed all affected lettuce from its menu.

More than 3,000 customers have used the product and at least 94 people have been hospitalised, yet no fatalities have been reported.

The recall covers over 27 states and includes Marketside-branded iceberg lettuce sold at Walmart locations. State health authorities are still investigating how the parasite entered the supply chain.