(NewsNation) — Police in Boulder, Colorado are investigating an overdose death they say was caused by a drug 10 times more powerful than fentanyl.

The drug is part of a group of drugs known as nitazenes. It’s nicknamed “Frankenstein” and was developed in the 1950s, but the Food and Drug Administration never approved it for consumer use.

Like fentanyl, it’s a synthetic opioid, but it’s even more potent than regular opioids. The Alcohol and Drug Foundation says the drug is 10 times more potent than fentanyl and often comes from China. They believe it is being sold on the dark web.

An undercover agent overseeing the case of the Colorado overdose told NewsNation it took coroners weeks to figure out.

“After having trouble because nothing was showing up on the different types of toxicology [reports], then they handed it to another lab to do an in-depth one and they were able to find out that it was that nitazene,” the agent said.

The drug is called N-Desethyl, part of a class of drugs known as nitazenes. It’s a type of opioid that was originally created to act as a substitute for morphine.

Law enforcement officials say today, people are illegally purchasing the drug online to take or resell. Investigators are calling the distribution of nitazenes more “surgical” than the widespread networks that help distribute fentanyl.

“People can have drugs mailed to them or their business and then they can either take the drugs themselves or they deal in these dangerous drugs and other people unfortunately could be exposed, ingest it and die or have medical complications,” the undercover agent said.

That makes it more challenging for officers to crack down on those selling it.

Not much is known about the drug but investigators say more is coming to light every day. One small study did show the potent drug requires a higher dose of overdose reversal drugs like naloxone than fentanyl and there is no guarantee of survival.