According to the report, Immigration and Customs Enforcement found the cars at the Ford Rail Distribution Facility in Woodhaven, Michigan, just south of Ford's world headquarters in Dearborn. ICE became involved after a Ford employee reported the cars to Woodhaven police.
It's unclear when and where the cars were packed with marijuana. With the cars in Minnesota, it's believed that the weed was added after leaving the factory but before being loaded on the train. Spare tires were removed and the space was used to smuggle the marijuana.