COLUMBUS (AP) — 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.

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.