PHILADELPHIA -- Federal agents on Thursday raided a Boeing plant that makes military helicopters in a Philadelphia suburb and charged more than three dozen people with distributing or trying to get prescription drugs, among them powerful painkillers.

The arrests were made by the FBI and the Drug Enforcement Administration at the 5,400-employee plant in Ridley Park, where workers build aircraft including the H-47 Chinook helicopter and the V-22 Osprey.

The plant, part of Boeing's Defense, Space and Security unit, is also the headquarters for its Rotorcraft division.

It did not appear to be an organized drug ring, but rather a "nebulous" series of independent actors, according to authorities.

"These sales placed the individual abusers, as well as society at large, at risk," said DEA agent Vito Guarino.

Thirty-six of the 37 people charged were current or former Boeing employees, U.S. Attorney Zane Memeger said at a news conference.

He did not know what kind of jobs they had, and he said he wasn't aware of any accidents or problems involving aircraft made by the suspects.

Indictments were unsealed charging 23 people with illegal distribution of a prescription drug, according to federal prosecutors.

In addition, 14 others were charged with attempted possession of the various drugs -- including the painkillers fentanyl, oxycodone and others -- allegedly being sold by their co-workers.

Prosecutors said 36 of those charged had been arrested, but they declined to comment on the status of the 37th.

Boeing informed authorities of its suspicions about drug activity on the property after an internal investigation, company spokesman Damien Mills said in a statement.

Employees are tested if they are suspected of being under the influence of drugs or alcohol, the statement said.

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A man who answered the telephone at the union for workers at the plant declined to comment.

A message left for a spokeswoman for the Department of Defense was not returned.

Prosecutors said they don't think there was any connection between the drug arrests and a 2008 error at the plant.

In November of that year, Boeing temporarily shut down two production lines that make the Chinook and Osprey after a plastic cap was found in the fuel line of an in-production Osprey.

Boeing later submitted a corrective action plan and restarted production.