Coroners in two of Ohio’s largest counties have issued drug abuse warnings following the reappearance of an opioid so powerful it’s sometimes used to sedate elephants.

Dr Anahi Ortiz is coroner in Franklin county in central Ohio. She said Friday that the county which calls Columbus home had at least three carfentanil-related overdose deaths in January.

Ortiz said the county saw six carfentanil-related deaths in all of 2018, with the last in September.

Ortiz says the drug is “extremely potent” and almost impossible to detect by sight because it’s often mixed with other drugs such as cocaine or heroin.

The Cuyahoga county medical examiner Dr Thomas Gilson issued a similar warning Thursday based on an increase in carfentanil seizures in the Cleveland area this year.

Drug overdoses killed more than 72,000 people in the United States last year – a new record driven by the deadly opioid epidemic, according to data from the Centers for Disease Control (CDC).

The CDC estimates that 72,287 people died from overdoses in 2017, an increase of about 10% from the year before. A majority of the deaths – nearly 49,000 – was caused by opioids, according to the new data.