More than three dozen people have been charged in a prescription drug sweep that included a raid on a Boeing plant near Philadelphia that makes military helicopters.

The arrests happened Thursday morning at the 5,400-employee plant in Ridley Park.

Federal authorities say 37 people are facing charges including illegal drug distribution and attempted drug possession. They say 36 of them are employees or former employees of the Boeing plant.

U.S. Attorney Zane Memeger says the arrests are the result of a four-year undercover investigation. He says Boeing contacted authorities to report "suspicions that drug activity was occurring on their property."

An official with Boeing's Military Aircraft division at the plant declined to comment. A message left for a defense unit spokesman was not immediately returned.