A group of United Parcel Service (UPS) employees are accused of smuggling shipments of drugs and counterfeit vaping oils from Mexico and distributing the illicit products around the U.S. for at least a decade.

Authorities arrested 11 people, including four UPS drivers and supervisors, in Tucson, Ariz., for their roles in the alleged smuggling ring, the Department of Homeland Security said. Investigators say the suspects moved thousands of pounds of marijuana and other drugs into the U.S. from Mexico each week using the company's standard cardboard boxes, bypassing security measures.

Mario Barcelo, a 20-year UPS employee and dispatch supervisor -- was named as the alleged ringleader of the operation. In a news release, the federal authorities said officials learned of the operation in 2017. Barcelo was arrested on Nov. 13.

Prosecutors said Barcelo, 49, used his position in the Tucson UPS distribution facility to ensure the drug shipments were loaded to the correct trucks and delivered to the intended destinations. Authorities in Tucson had been investigating Barcelo since 2009, The Washington Post reported.

However, they became frustrated when UPS would not cooperate with them to intercept and prevent potential crimes. They cited a 2017 incident in which they were prevented from entering the Tucson facility after learning of an illicit shipment.

In a statement to Fox News, UPS said it is cooperating with law enforcement but is “not at liberty to discuss the details of the arrests as this is an ongoing investigation.”

Aside from Barcelo, UPS supervisor Gary Love and drivers Michael Castro and Thomas Mendoza are charged with money laundering, drug possession and drug distribution. Seven others are facing charges on shipping drugs and operating stash houses.

Raul Garcia Cordova, 47, faces more than a dozen charges. A police raid at his home turned up 50,000 counterfeit vaping pens, a Chevrolet Corvette and a Range Rover.

Prosecutors said Barcelo and the alleged suspects expand their operation from delivering marijuana to more lucrative drugs and black-market vaping pens.

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Undercover officers posing as drug traffickers contacted Barcelo to ship a fake shipment of cocaine in 2018 and 2019. Trackers were placed inside boxes containing the products to documents its movement and the phones of UPS employees were tapped.

Police also obtained video footage of the group coordinating the operations.