File Photo

McALESTER, Okla. (AP) — The state medical examiner says a 20-year-old woman who died at an Oklahoma rehabilitation center died from an accidental drug overdose.

Stacy Murphy was found dead in July at Narconon Arrowhead near McAlester. Medical examiner's spokeswoman Amy Elliott tells the McAlester News-Capital that Murphy died from acute oxymorphone toxicity. Oxymorphone is a narcotic painkiller.

Murphy is one of four patients who've died at Narconon since 2009. Her parents have filed suit against Narconon, alleging that the facility's actions were "grossly negligent."