Metro Nashville Police detectives found a drug used to cut heroin in the mail.
Police and postal inspectors found the carfentanil in a piece of mail Wednesday after receiving a tip. The drug is legally used as an elephant tranquilizer.
The drug was found in a package and found the packet containing 140 milligrams of the drug. It may not sound like a lot, but that's enough for thousands of lethal human doses.
Investigators didn't know who sent the package, and who it was meant for.
Carfentanil is 10,000 times more potent than morphine and is responsible for many overdose deaths throughout the U.S.