India, July 15 -- Several Taco Bell restaurants in metro Detroit have stopped serving lettuce and cilantro as Michigan investigates a growing outbreak of cyclosporiasis, a parasitic illness that has sickened 3,309 people across the state as of July 14.

Employees at six Taco Bell locations in Trenton, Woodhaven, Wyandotte, Taylor, Riverview and Southgate said that the fresh produce items were no longer being offered. Neither Taco Bell nor public health officials have linked the restaurant chain to the outbreak.

Michigan health officials said their investigation is increasingly pointing to lettuce and other salad greens as a possible source of the infections, although they have not identified a specific product, grower or supplier. State Ch...