US public officials are blaming a Salmonella outbreak on an unlikely source: kratom, a plant known for its opiate-like effects. The outbreak began in October, and by the end of January, infections cropped up from California to Massachusetts, according to the Centers for Disease Control and Prevention.

So far, no one has died from this latest outbreak, but 11 people have been hospitalized. The CDC reports that it’s confirmed 28 people in 20 states have contracted the strain of Salmonella, which gives people diarrhea, fever, and abdominal cramps. Public health investigators discovered that the cases were linked when they sequenced the DNA of Salmonella samples collected from the patients. The bacteria were genetically related, which means that the patients probably all contracted Salmonella from the same place.

Public health investigators interviewed the patients, and discovered that several had recently taken kratom in pill, tea, or powder form. The CDC hasn’t tracked the infections back to a single brand or supplier yet. So the agency recommends that “people not consume kratom in any form.”

The US Drug Enforcement Agency is considering banning kratom — and the Food and Drug Administration is cracking down on kratom in dietary supplements. People who take kratom report that it can help ease opioid withdrawal, and scientists are investigating the plant’s psychoactive compounds to develop better painkillers. That doesn’t mean it’s safe, though. Poison control centers receive hundreds of calls about kratom each year, and that number is climbing, the Food and Drug Administration says. At least 44 deaths have been linked to the plant.

But this is the first time the drug has been linked to a bacterial outbreak — though not the first time Salmonella has spread through plants. Salmonella, which usually spreads through feces, can make its way to plants through runoff contaminated with poop. (It can also show up during the manufacturing and packaging process, if someone sick is handling the plants there.) While the infection typically clears up on its own in about a week, Salmonella can be especially dangerous to children, the elderly, and people with weak immune systems.