The arrests come as Illinois works to combat a statewide K2 epidemic that as of Monday had killed two and sickened nearly 60 others, public health officials said.
The drug can cause users to bleed uncontrollably from their eyes, nose and gums.
"The synthetic cannabinoids were packaged in sealed containers and labeled with such names as 'Matrix,' 'Blue Giant' and 'Crazy Monkey,’" federal agents said. "Preliminary testing of some of the cannabinoids purchased by the undercover officer revealed a detectable amount of brodifacoum, a toxic substance frequently used in rat poison."
Federal investigators said the men sold between 50 and 60 packets of the drugs per day from the King Mini Mart convenience store, located on Chicago’s west side. One of the men, Masoud, had $280,000 in his possession, according to federal drug enforcement agents.
Multiple people recently experienced adverse symptoms, including unusual bleeding, after using synthetic cannabinoids obtained from the store, according to the complaint.
The store workers are each charged with conspiracy to knowingly and intentionally possess with intent to distribute, and to distribute, a controlled substance.
The men are in custody and awaiting court hearings. It wasn't immediately known if they had obtained legal representation.