According to new research, synthetic marijuana has recently been linked to various illnesses and even death. Doctors in Colorado are sending out warnings about the products due to a recent surge in reported illnesses connected to synthetic marijuana use.

According to Health24, the synthetic products have come under investigation after a reported 263 people went to the emergency room throughout Colorado in one month. Common complaints from patients were irregular heartbeats, seizures, and an altered mental status.

Health24 reports that Dr. Andrew Monte, an assistant professor in emergency medicine at the University of Colorado School of Medicine in Denver, said, β€œAt the end of August, we started noting that patients were coming in with a very severe clinical illness.”

Although synthetic marijuana is illegal it is still available at public stores. According to Medical Express, synthetic marijuana is sometimes labeled as incense, potpourri, or herbal smoking blend. It is sold in gas stations and convenience stores under a variety of brand names including Black Mamba, K2, and Spice.