Kentucky state police arrested 17 General Motors workers at the Chevrolet Corvette plant in Bowling Green, Ky., on drug charges.
After a 14-month undercover investigation, officers entered the plant at 7 a.m. on May 7 to arrest 15 workers.
Officers returned later in the day with police dogs in search of more drugs.
Two other workers were arrested at that time for possession of marijuana.
The first 15 face 51 counts of drug possession and trafficking charges.
According to an officer with the Kentucky State Police, the investigation was prompted by complaints from other employees that some workers were consuming and selling drugs on the job.
GM responded to the complaints by hiring an outside security firm, ASET Corp. of Dayton, Ohio, to investigate.
GM has used ASET for drug investigations at other U.S. plants.
The Kentucky State Police say the investigation is now closed.