MINNEAPOLIS (AP) — Minnesota authorities say the dangerous drug carfentanil is to blame for five recent overdose deaths, and could be a factor in up to five additional cases.

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 recent overdoses around the country.

The five confirmed carfentanil overdoses in Minnesota happened from Jan. 30 through Feb. 17 in Minneapolis, Apple Valley and Faribault. The victims ranged in age from 23 years old to 43 years old.

Authorities say these are the first known carfentanil deaths in the state, and the issue is being considered a health crisis.