The CDC is warning people to avoid taking the popular yet controversial herb kratom.

Already in the FDA’s crosshairs for its opioid properties, kratom has now been identified as the culprit behind a salmonella outbreak that has sickened more than two dozen people in 20 states. Eleven of those were affected to an extent that required hospitalization.

“At this time, CDC recommends that people not consume kratom in any form. The investigation indicates that kratom products could be contaminated with Salmonella and could make people sick,” the CDC says on its website. The agency conducted interviews of the salmonella sufferers to determine their exposures prior to getting sick.

Salmonella is a foodborne illness that causes 19,000 hospitalizations and 380 deaths annually in the U.S. Symptoms include diarrhea, fever, and abdominal cramps.

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FDA says popular herbal drug is dangerous opioid

Kratom is used both recreationally, for its stimulant effects, and by people who claim that it’s an effective remedy for opioid addiction – a claim vigorously disputed by the FDA, which says it actually has opioid properties.

The American Kratom Association calls the substance “a safe herbal supplement” similar to coffee and tea.

While kratom is illegal in a number of states and local jurisdictions, it is available online and in some stores.