A federal investigation conducted by the U.S. Food and Drug Administration (FDA) determined that the contamination originated from a Mexican lettuce supplier, whose products were used by Taco Bell restaurants in five U.S. states, according to a CDC statement.

More than 1,644 people across Indiana, Kentucky, Michigan, Ohio, and West Virginia have been diagnosed with cyclosporiasis, a parasitic illness that can cause severe gastrointestinal symptoms, including explosive diarrhea, the CDC said.

The outbreak has resulted in 94 hospitalizations. According to the CDC, all of the reported cases have been linked to contaminated lettuce purchased from Taco Bell.

“The specific ingredient supplied by this vendor has been removed from our national supply chain indefinitely and will be replaced within 24 hours in certain states,” Taco Bell said in a statement.

“We believe protecting public health is a shared responsibility among restaurants, suppliers, and public authorities, and we are proud to act quickly and proactively to protect our customers,” the company added.

If left untreated, cyclosporiasis can last for more than a month and may lead to dehydration, although it is generally not fatal.

Michigan has been particularly hard hit by the parasite this year, with authorities reporting more than 5,000 cases.