The U.S. attorney’s office in St. Louis announced charges Thursday against 27-year-old Ruben Lopez and 31-year-old Jonathen Aguilar, both of St. Charles, Missouri.

Federal prosecutors say investigators intercepted a suspicious mailing and discovered a one-kilogram “brick” of fentanyl hidden inside clothing. They say they also found guns and machines used to encapsulate drugs.

A second warrant was executed and found another kilogram of fentanyl at a second address.

Drug Enforcement Administration Special Agent in Charge William Callahan says the investigation removed more than 1.5 million potentially lethal doses of fentanyl.