An Arizona mother-son duo have been arrested in the Chicago area after allegedly attempting to smuggle thousands of fentanyl pills through an Illinois suburb, police said.

Gloria Gastelum, 54, and German Vargas, 22, were arrested when McHenry County sheriff’s deputies stopped them as they were driving through Marengo on Thursday, officials said in a Facebook post:

The traffic stop was made after the McHenry County Sheriff’s Narcotics Task Force received information from an undercover detective that a “large quantity of illegal narcotics would be entering the area” that day. 

Deputies stopped the mother and son while they were driving in a rental car, allegedly finding them in possession of 120,000 fentanyl pills marked as oxycodone. 

“Gastelum and Vargas were arrested and taken into custody without incident,” the sheriff’s office added.

The pair, both from Tucson, Arizona, were each charged with manufacturing and delivering 900 grams or more of fentanyl  and possession of 200 grams or more of fentanyl.

“[McHenry County Judge Carl] Metz said that both defendants are flight risks because they are allegedly part of a large drug organization based in Sonora, Mexico, and have the means to avoid prosecution by crossing the U.S.-Mexico border,” according to the Lake and McHenry County Scanner.