WASHINGTON (AP) — Federal health officials on Friday said they have linked cases of a diarrhea-causing parasite tied to shredded lettuce to an additional four states, expanding the scope of the largest U.S. outbreak of cyclospora.

The Centers for Disease Control and Prevention said the outbreak first tied to Taco Bell restaurants now includes Illinois, Kansas, Oklahoma, and Pennsylvania. Previously the agency's investigation included five states: Indiana, Kentucky, Michigan, Ohio and West Virginia.

The CDC, Food and Drug Administration and state health officials have been tracing the supply of the lettuce and interviewing people across the nation about the foods they ate two weeks before getting sick.

The number of cases linked to lettuce served at Taco Bell is now 1,947, including at least 98 people who had to be hospitalized. There have been no deaths, the agency reported on its website.

The total number of people sickened by the outbreak is likely higher than the official tally, given that not all cases are reported, the agency noted.

FDA officials earlier this week said they remain focused on lettuce from Taylor Farms as the source of the multistate outbreak. The company last week announced it was recalling iceberg lettuce grown in central Mexico.

On Thursday, the FDA announced it was investigating a separate outbreak of cyclospora reported in 72 people. Regulators had not yet identified the products linked to the illnesses.

Overall, cyclospora cases have set a U.S. record. Since May 1, CDC has received reports of more than 4,100 laboratory-confirmed cases and is investigating more than 7,400 other likely cases across 41 states. Federal health officials have said that other “brands, restaurants, retailers, or distribution channels” could be tied to the outbreak as the investigation continues.

Cyclospora is a microscopic parasite that infects food that has come into contact with human feces, most commonly when produce is irrigated or washed with contaminated water. When ingested, the parasite causes intestinal illness marked by “frequent and sometimes explosive bowel movements,” according to the CDC.

On Thursday, Mexico health officials announced that the parasite was not detected in the lettuce or water at the Taylor Farms plant in the Mexican state of Guanajuato.

The results were announced following a visit by Mexican health authorities to the Taylor Farms plant between July 18 and 20, during which 10 samples of iceberg lettuce were collected. Four water samples also were collected for analysis, authorities stated.

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Fabiola Sanchez contributed to this story from Mexico City

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