The U.S. Justice Department says three dozen current and former workers at a Boeing factory in the northeastern state of Pennsylvania have been arrested for illegally selling or buying prescription drugs.

Agents from the FBI and Drug Enforcement Administration raided a plant Thursday owned by U.S. aviation giant Boeing that builds aircraft for the U.S. military. Prosecutors say 23 people have been charged with selling prescription drugs, including the powerful painkiller oxycodone. Another 14 people have been charged with attempting to possess the drugs allegedly being sold by their co-workers, which is a misdemeanor.

A spokesman for Boeing says the company informed federal investigators in 2007 of possible illegal drug activity at the plant, after conducting its own probe the year before.

U.S. Attorney Zane Memeger told reporters the investigation focused on both the alleged sellers and users “because of the critical role these employees play in manufacturing military aircraft.” Memeger said there was no evidence of problems with any of the aircraft made by the employees.

All but one person arrested in the case had been employed at the Boeing plant.