ST. CHARLES (KMOX) -- Off the streets of St. Charles County over the last couple of days: enough fentanyl to kill 400,000 people.The larger of the two busts took place around 3:30 Tuesday morning when officers pulled over a moving truck for traffic violations on Interstate 70.St. Charles County prosecutor Tim Lohmar says an officer found nine kilograms of cocaine and two kilograms of fentanyl in an air compressor in the back of the truck."He just knocked with his knuckle on the, uh, the tank portion of the compressor," Lohmar told reporters. "The sound that came out didn't sound like you would think it would -- it had more of a thud sound as opposed to a ring."The other bust occurred early Monday morning when officers pulled over a mother and son for traffic violations. They smelled pot and found in their car two pounds of heroin.All the drugs combined worth more than $440,000. Lohmar guesses they were heading from the west coast to the east coast.