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, a source familiar with the investigation told CBS News on Thursday.

The source said a traceback investigation by the Food and Drug Administration identified a single supplier of iceberg lettuce from Mexico, Taylor Farms, that was used by Taco Bell locations in five states where people who contracted cyclosporiasis ate. The FDA is investigating, the source said. 

Taylor Farms, based in Salinas, California, is a supplier to several major restaurant chains across the U.S. CBS News has reached out to Taylor Farms and Taco Bell for comment. 

The outbreak, a diarrheal illness caused by the parasite cyclospora, was first reported in early May and has since spread to 34 states, according to the latest numbers from the U.S. Centers for Disease Control and Prevention.

It has sickened at least 1,645 people, per CDC data, including at least 141 hospitalizations. There have been no reported fatalities so far.

The majority of the cases have been reported in Michigan.

Earlier this week, Taco Bell said in a statement that it had “voluntarily and temporarily removed limited ingredients at select restaurants as a precautionary measure” as a result of the outbreak.  

Last year, an E. coli outbreak was linked to onions provided to several restaurants from a Taylor Farms facility in Colorado. As a result, McDonald’s was briefly forced to stop using onions on its Quarter Pounders at some locations.

On its website, Taylor Farms bills itself as the “leading global producer of salads and healthy fresh foods, with production facilities across the U.S., Canada, Mexico, and Western Europe.”