Severe side effects that caused two deaths and dozens of illnesses in Illinois have been tentatively linked to tainted synthetic pot. The horrific side effects included internal bleeding, severe bloody noses, and bleeding gums. The incidents occurred in the Chicago area and central Illinois in the past month. Investigators believe that the synthetic pot was tainted with rat poison.

Ninety-five people have been hospitalized since early March with similar symptoms. Most of the Chicago patients showed signs of internal bleeding, including abdominal pain and blood in the urine or stool. Most of the patients reported smoking synthetic pot, while others vaped the drug or drank it in tea. Patients started seeing symptoms within days of using the synthetic drugs.

Investigators say users had been using different brands of the synthetic pot, but are trying to trace whether the drug is from a single source. It’s possible that the tainted drugs ended up in different packaging under various brand names. The Centers for Disease Control and Prevention is sending a team to help the Illinois Department of Public Health investigate the outbreak.

Synthetic pot is created by spraying a man-made mixture of hundreds of chemicals onto plant matter. The chemicals affect the same brain cell receptors as the active ingredient in marijuana. The compromised plant material, often sold and branded as “K2” and “Spice,” is then smoked. The chemicals are also sold in a liquid form to be used in e-cigarettes or vaping devices.

People use synthetic pot because it’s relatively cheap and isn’t detected on drug screenings, but using the products can be dangerous. The man-made drugs are manufactured without being tested by any credible source. Because laws to ban synthetic pot prohibit specific chemicals, manufacturers keep tweaking their recipes to keep their drugs on the market. There is no way for users to tell what is in the batch of synthetic pot they bought.

At least nine of those who fell ill in Illinois tested positive for brodifacoum, commonly sold as rat poison. Exposure to rat poison causes the body to block its natural use of vitamin K, preventing proper blood clotting. Further testing is needed to see if any of the others have also had exposure to the poison.