The recent surge in overdoses from the potent opioid carfentanil is overwhelming first responders and crime labs in Ohio, NPR reports. Carfentanil, used to sedate elephants, is 100 times stronger than fentanyl.

The rate of carfentanil overdoses in Ohio is averaging 20 to 25 a day. The Drug Enforcement Administration says the drug has only been confirmed in Ohio and Kentucky. Other states are starting to test for it.

“It’s what we don’t know about this drug that scares us,” says Dr. Lakshmi Sammarco, the coroner for Hamilton County, Ohio. “We don’t have any human testing data. We don’t know what the lethal level really is. There is no therapeutic level — it’s not meant for human use.”