Investigators are struggling to figure out why drugs keep ending up inside brand-new Ford Fusions after police in Ohio discovered $1 million worth of weed hidden in the cars' trunks, CNN reports.

The DEA's Silverio Balzano told CNN the 15 pot-laden Fusions were made at a plant in Mexico before Ford packed them onto a train and shipped them to Ohio and Pennsylvania. Once they arrived at a dealership in Youngstown, employees discovered 32 pounds of marijuana in the cars' trunks, stuffed into the spare tires' wheel wells.

A Ford spokesman told CNN there's no way the weed made it into the Fusions at its Mexico plant or its internal shipping yards—prompting investigators to wonder who the hell packed it in, when they did it, and why they didn't take it out before the cars made it to a dealership.

"Clearly, something went wrong," Balzano told CNN. "Generally speaking, they could take it off anywhere else along the way."

This isn't the first time authorities have discovered drugs in brand-new Ford Fusions. In addition to this latest bust, cops have confiscated at least 250 pounds of weed from at least 22 Fusions in the early months of 2017, according to Alpha News and the Associated Press. Authorities first found 80 pounds of pot in the cars in February, at a rail yard in St. Paul, Minnesota. A month later, they uncovered a similar load from a yard about 250 miles away, in Dilworth, Minnesota. But investigators are still at a loss as to who's behind the operation and how they're pulling it off.

According to Alpha News, the Sonora district in Mexico that houses Ford's plant is controlled by the Sinaloa cartel—made famous by its former ringleader Joaquín "El Chapo" Guzmán. A source knowledgable about US customs processes told Alpha News they figured the smuggling operation might have been orchestrated by a cartel.

"The plant assembly employees sometimes only make $50 a week, leaving a huge window for bribery," the source said. "It's not unheard of for impoverished foreign nationals to take payoffs, especially since what the cartels can pay may equal a year's worth of wages or if they threaten the employee or their family."

"We're aware of the situation and are taking it very seriously," a Ford Motor Company spokesman told CNN. "We are working with the FBI and Customs on an extensive investigation."