Federal officials expressed their concern regarding a new opioid mix circulating the streets of the U.S. The new mix, dubbed as "gray death," is said to be more potent than heroin and can be fatal if touched.

"Gray death is one of the scariest combinations that I have ever seen in nearly 20 years of forensic chemistry drug analysis," said Deneen Kilcrease, manager of the chemistry section at the Georgia Bureau of Investigation, in a report from Chicago Tribune.

Gray death is a combination of several opioids, including heroin, fentanyl and carfentanil. Also included in the mix is U-47700, a synthetic opioid listed in the category of most dangerous drugs by the U.S. Drug Enforcement Agency.

A bulletin issued by the Gulf Coast High Intensity Drug Trafficking Area showed that gray death has much higher potency than heroin. Due to the strength of the new drug and the ability of the skin to absorb it, experts noted that simply touching gray death could be dangerous.

Usually appearing to be like concrete mix, gray death may vary in consistency -- from hard, chunky to a fine powder. Experts are still not sure of the exact ingredients and concentration of gray death. Due to this, it is highly possible that users of gray death don't have the slightest clue of what they are taking. Users may get the high they seek by injecting, swallowing, smoking or snorting the new opioid mix.

So far, gray death was only detected or has been reported to be a cause of overdose in Georgia, Alabama and Ohio. In 2016, U-47700 was associated with dozens of overdose cases in New York and North Carolina. In the past three months, there have been at least 50 overdose cases in Georgia involving gray death.

According to the Centers for Disease Control and Prevention, opioid overdose killed more than 33,000 people in the U.S. in 2015.