MINNEAPOLIS — Minnesota authorities said Thursday that the dangerous drug carfentanil is to blame for five recent overdose deaths in the state, and could be a factor in up to five additional cases where confirmation is pending.

The confirmed overdoses represent the first known carfentanil deaths in Minnesota, said Andrew Baker, chief Hennepin County Medical Examiner. The five overdoses happened from Jan. 30 through Feb. 17 in Minneapolis, Apple Valley and Faribault, and the victims ranged in age from 23 years old to 43 years old.

Authorities said they consider the discovery of carfentanil to be a public safety issue. Law enforcement agencies and emergency responders are being alerted, and those who battle opioid addiction are being told to watch out for each other.

“It is unclear at this point what threat this really represents,” said Jon Cole, an emergency physician and medical toxicologist at Hennepin County Medical Center and medical director of the Minnesota Poison Control System. “We know enough to know that this drug is ultra-potent. And we know enough to know that we should be concerned.”

Carfentanil is a synthetic opioid that’s used as an elephant tranquilizer. It’s 10,000 times more potent than morphine and 100 times more potent than fentanyl. According to information from the U.S. Drug Enforcement Administration, carfentanil is often disguised as heroin and has been blamed in clusters of overdoses around the country.

Ken Solek, assistant special agent in charge of the DEA in Minnesota, said the drug is so strong that it can’t be diluted enough for safe human consumption, and many people don’t realize they are taking it.

Baker said the five confirmed carfentanil cases were clear overdose deaths, but routine toxicology testing did not identify a cause of death. More testing was done by a specialized reference laboratory, which detected the carfentanil. Those results came back over the course of the last week.

Authorities will be working together to try to determine if the drug is from the same source. But for now, Solek said, the investigation is just getting started.

“This could just be a one-time incident … we don’t know what this is yet,” he said.