Drugs that caused three recent overdoses in a Minnesota city were found to have contained traces of the elephant tranquilizer carfentanil.

Northfield Police Department shared the lab results it got back from the Minnesota Bureau of Criminal Apprehension regarding illegal pills linked to the overdoses.

What's particularly worrying is that the pills were bought illegally and that the buyers were under the impression they were getting "Oxy" – a common nickname for opioid painkillers like Oxycontin, Oxycodone or Percocet.

The drugs had been manufactured to look like real Oxycodone 30mg pills, police say, but actually contained the powerful and deadly opioid carfentanil – as well as cocaine.

Carfentanil is up to 10,000 times more powerful than morphine and has been responsible for hundreds of fatal overdoses across the U.S.

Fortunately, the Northfield cases were nonfatal, with naloxone used to revive the victims, but carfentanil was behind at least 11 overdose deaths in three Twin Cities counties last year in the space of just a few months.

Joshua Edward Tarka, 22, has been charged with three counts of great bodily harm caused by distribution of drugs over the Northfield overdoses, as well as facing drugs charges.

The drug's potency

It comes as concern as the opioid crisis continues to grow, with carfentanil abuse being one of the most alarming new trends. It's a synthetic drug that is 10,000 times stronger than morphine, about 3,000 times stronger than heroin and 100 times stronger than fentanyl (which has also been linked to a string of overdose deaths, including that of Prince).

Carfentanil, which is commonly used to drug elephants and other large animals, cannot be detected by routine drug and alcohol screenings, so samples need to be sent to a specialized lab for testing.

It's so powerful that first responders and police officers responding to a possible overdose can be harmed if they're exposed to the drug, which can be absorbed through the skin or accidentally inhaled.

It comes in several forms including powder, blotter paper, tablets, patches and spray, according to the U.S. Drug Enforcement Administration.

It only takes a very small amount – think a few grains of salt – to tranquilize an elephant, with officials noting the drug cannot be diluted enough to be safe for human consumption.