BAKERSFIELD, Calif. (KGET) — More than a dozen people have been arrested and charged in a massive illegal drug trafficking operation in Fresno County, resulting in the seizure of more than 50-thousand counterfeit pills.

The announcement comes from U.S. Attorney Phillip Talbert Friday morning, following the conclusion of “Operation Killer High,” which was launched after a string of fentanyl-related overdoses in Fresno. Officials said that out of every 10 pills seized, at least four contained fentanyl a powerful and often lethal synthetic pain killer.

Many were made to look like prescription pills.

“Greed is what drives these criminals who manufacture, transport and sell highly illicit and highly addictive drugs. The more addicted the end user becomes, the more they purchase and the more profit that is realized by the criminals,” Fresno County District Attorney said.

The 18 defendants are being charging with trafficking fentanyl powder, fentanyl pills, cocaine, and methamphetamine.