The FDA is investigating iceberg lettuce supplied to Taco Bells by Taylor Farms as a possible source in an escalating outbreak of cyclosporiasis in four Midwestern states.

Taco Bell has pulled certain ingredients from some locations amid the outbreak of parasitic infections causing "explosive" diarrhea across the U.S.

US health authorities are examining whether Taco Bell locations are linked to a major Cyclospora outbreak centred on Michigan. The probe has yet to identify a specific source, though lettuce and other leafy greens are under scrutiny.