A sample of iceberg lettuce from food supplier Taylor Farms tested positive for the parasite that caused an explosive outbreak of diarrhea that affected thousands of people in the U.S., officials said.

The Food and Drug Administration (FDA) said Taylor Farms, which supplies the Taco Bell food chain, had confirmed that the sample was taken from a product that is not part of its current recall announced Friday.

The agricultural company announced Friday that it would voluntarily withdraw all iceberg lettuce from central Mexico from the U.S. market and issued a list of affected products.

No deaths have been reported, but at least 94 people have been hospitalized due to cyclosporiasis infections.

A recall differs from a voluntary removal of a product in that it requires a company to notify customers and recall affected products from commerce, making it a more extensive and costly corrective action.

The FDA said it collected the sample during targeted import surveillance as part of its investigation into the outbreak.

“Taylor Farms has confirmed that this positive product is not part of its current recall,” the FDA said. “They are currently working to identify whether any part of this implicated batch is available in commerce or in consumers’ homes.”

According to the FDA, the infections were first detected on May 13.

Symptoms of foodborne illness can take up to two weeks to appear. They include watery diarrhea that lasts for days, sudden weight loss, and loss of appetite.

Thousands of people have been infected with Cyclospora linked to iceberg lettuce supplied by Taylor Farms and sold at Taco Bell locations in at least five states, according to the Centers for Disease Control and Prevention (CDC).

The CDC recommends not eating the shredded iceberg lettuce served at Taco Bell locations in Indiana, Kentucky, Michigan, Ohio and West Virginia.

The fast food chain said it had completed the removal of the affected Taylor Farms lettuce from its restaurants.

In a statement, Taylor Farms said it “stopped receiving products from the involved lot and suspended distribution of iceberg lettuce from central Mexico,” it said. [its] clients and [is] “continuing to work with the FDA, CDC and state authorities.”

The lettuce was removed , external in 27 states. It also includes Marketside brand iceberg lettuce sold at Walmart locations in 15 states, according to the FDA.