A lettuce supplier to fast-food giant Taco Bell is being investigated as a possible source for a nationwide cyclosporiasis outbreak that has sickened thousands of people.

The cyclosporiasis outbreak has sickened thousands of people nationwide, and Michigan has been the hardest hit.

Taco Bell has removed several fresh ingredients, such as lettuce, from its menus at locations across the country, including in Texas and Michigan.

Nearly 7,000 cases of cyclosporiasis have been reported across the country

Upwards of 1,600 people who contracted cyclosporiasis reported eating at the chain beforehand, the CDC and FDA said.