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NORRISTOWN, Pa. (CBS/AP) — A Pennsylvania prosecutor says a fourth doctor has been arrested for unlawful prescribing and other charges as part of a months-long investigation into area physicians accused of overprescribing drugs.

Montgomery County officials along with federal Drug Enforcement Agency officers announced Wednesday that 48-year-old Lansdale physician Lawrence Miller was arrested and arraigned on 51 counts. Officials say nine of his patients had died of overdoses that often included a mix of the prescribed medication that was accompanied by little or no medical treatment and street drugs.

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From left to right; top to bottom: Lawrence Miller, Joseph Cipriano, Brian Keeley and Joseph Rybicki (Credit: Montgomery County District Attorney’s Office)

“Nine of miller’s patients died of drug overdoses–dead from a combination of street drugs,” said Montgomery County District Attorney Kevin Steele.

Officials say the three other physicians, Brian Keeley, Joseph Cipriano and Joseph Rybicki were arrested and charged with similar counts in February, May and July.

Cipriano is accused of trading highly addictive narcotics prescriptions for some action on Snapchat.

“He does this in exchange for nude photographs, videos or sexual favors,” said Steele.

Court records show doctor Rybicki had been evicted from his practice. So he opened a concierge service, operating his own mail-order service, and it’s alleged his wife handled the business end.

“He attempted to conceal the crime by issuing prescriptions in his daughter’s name,” said Steele.

And Keeley allegedly set rates for his narcotic prescriptions. A month’s worth for $180.

Records show his practice was so dirty, it was condemned after agents searched the place.

(© Copyright 2018 CBS Broadcasting Inc. All Rights Reserved. The Associated Press contributed to this report.)