US fast food chain Taco Bell is removing lettuce from its menu in some states after investigations found it could be linked to an outbreak of explosive diarrhea caused by a parasite.

The decision was made “out of an abundance of caution” after discussions with health officials, Taco Bell told the BBC.

The Centers for Disease Control and Prevention (CDC) says 1,645 people in five states who reported “exposure” to Taco Bell have been infected by cyclosporiasis, a parasitic infection that spreads through contaminated food or water.

“Do not eat foods with shredded Mexican iceberg lettuce served at Taco Bell locations in Indiana, Kentucky, Michigan, Ohio, and West Virginia,” the U.S. Food and Drug Administration (FDA) said.

No deaths have been reported, but 94 people have been hospitalized due to cyclosporiasis infections, which were first detected on May 13, the FDA added.

The company said lettuce from one of its suppliers will be recalled indefinitely and replaced.

“While no official notice has been issued, we believe public health is a shared responsibility between restaurants, their suppliers and authorities,” the restaurant said.

It did not identify which states will remove lettuce from menus, but the majority of infections have been reported in Michigan, where more than 3,300 cases have been detected.

Taco Bell did not identify where the lettuce allegedly linked to the outbreak came from, but US media has named the supplier as Taylor Farms. The BBC has contacted the company about the reports.

Symptoms of cyclosporiasis infections can take about two weeks to appear.

Watery diarrhea that lasts for days, sudden weight loss, and loss of appetite are some of the most common symptoms.

Experts have told the BBC that the parasite is notoriously difficult to track, a task possibly complicated in part by cuts to federal health agencies.

“This is not like spotting a needle in a haystack. It’s like spotting a microscopic portion of a needle in a haystack,” said Steven Manderach, executive director of the Association of Food and Drug Officials.

Madeline Halpert, Kayla Epstein and Grace Goodwin contributed to this report.