UPS employees exploited a 'vulnerability' in the company's security to run a massive smuggling ring that shipped drugs, cash and illegal vapes across the country for a decade, police say.

Mario Barcelo, 49, allegedly masterminded the scheme, using his role as a UPS supervisor in Tuscon, Arizona, to make sure the illicit packages were delivered on time to exact locations without being picked up by security measures.

Barcelo, who worked for the company for 20 years, was arrested last Tuesday and is now charged with more than a dozen counts ranging from money laundering, to drug possession and drug distribution.

Charged alongside Barcelo is fellow UPS supervisor Gary Love, 40, and UPS drivers Michael Castro, 34, and Thomas Mendoza, 47.

UPS supervisor Mario Barcelo (left) is accused of masterminding a smuggling ring that exploited a loophole in the delivery company's security to ship drugs and illegal vapes across the US. Also charged is fellow UPS supervisor Gary Love, 40 (right)

UPS drivers Thomas Mendoza, 47 (left), and Michael Castro, 34 (right), have also been charged with offences ranging from money laundering, to drug possession and drug distribution

Seven other men, who were not employed by UPS, have also been charged with offences related to the shipping of the drugs and operating stash houses for the illicit materials, the Washington Post reports.

They are: Fernando Navarro-Figueroa, 32, Raul Garcia Cordova, 47, Abraham Felix-Navarro, 27, Heriberto Martinez-Bojorquez, 24, Victor Molina, 32, Jonathan Gallegos, 26, and Martin Siqueiros 31.

Law enforcement in Tuscon said they began tracking Barcelo 2009, but were repeatedly frustrated by UPS's refusal to cooperate with their investigation.

When police raided the mansion of Raul Garcia Cordova, 47, they seized a boat, a Chevrolet Corvette, and a Range Rover

In 2017, investigators say they were prevented from entering a company facility in Tuscon despite learning of a potential shipment.

Investigators say the operation started out by shipping marijuana, then transitioned to more valuable drugs such as cocaine and illegal vaping pens of the kind that have been linked to deaths across the US as time went on.

The operation was allegedly shipping several thousands pounds worth of drugs per week at the peak of its operation.

Detectives say Barcelo used a 'simple method' to obscure the origin and destination of the packages, though refused to disclose more details because they fear the same method could be used by other traffickers.

In his role as a distribution supervisor he then made sure the parcels were loaded on to the correct trucks to be delivered at precise times and locations.

In order to break the ring, officers used undercover operatives to place fake orders for drugs and cash, then placed GPS trackers inside packages to trace where they were going.

Officers say the scheme operated out of this Tuscon distribution center for a decade, exploiting a 'simple method' to obscure the origin and destination of the packages

Investigators say the smuggling operation began with marijuana but expanded to include more valuable drugs such as cocaine, as well as cash and vapes, as the gang became more confident of their methods (file image)

They also uncovered WhatsApp groups being used by the gang to coordinate the loading, handling, shipping and retrieval of cash and boxes.

During a raid on a mansion belonging to one of the alleged gang members - Raul Garcia Cordova - last week, police say they seized a boat, a Chevrolet Corvette, a Range Rover and 50,000 counterfeit vape pens.

Ledgers, cash and marijuana were also found stashed underneath a Jacuzzi, local media reported.

Authorities say more arrests are likely forthcoming, as one of the men - Jonathan Gallegos - is suspected of being a member of a larger drug-trafficking organization in Mexico.

UPS said that it is now cooperating fully with law enforcement professionals and 'will continue to provide information as needed.'