Authorities say they've shut down several New York City medical clinics and arrested two dozen people in a scheme to sell more than 5 million prescription painkillers on the black market.

The arrests were announced on Wednesday by the U.S. attorney's office in Manhattan and the New York City special narcotics prosecutor.

Investigators say the pill ring relied on corrupt physicians who wrote thousands of unnecessary prescriptions for highly addictive oxycodone since 2011. They say the 5 million pills had a street value of at least $170 million.

Prosecutors say unruly crowds of people formed each morning at a Bronx clinic to pay up to $300 to see a doctor, who would then give them oxycodone prescriptions without doing exams.