Detectives say they intercepted a package at a UPS store on Aug. 30 that had been dropped off by 36-year-old Gabriel Beltran Lopez.
The package allegedly contained a kilo of powdered fentanyl.
Deputies then executed search warrants at a home in Arizona City and another in Eloy. They reportedly discovered two more kilos of powdered fentanyl and six kilos of cocaine.
"In total, the three kilos of powdered fentanyl is potent enough to make up to 3 million fentanyl pills, with a street value of $15 million or more," said the Pinal County Sheriff's Office.
Lopez is accused of sending drugs to New Hampshire, New York, Pennsylvania, and Nebraska.
Deputies booked Lopez into the Pinal County Jail on drug charges.