According to the Oklahoma Medical Examiner's office, the death of a 20-year-old patient at Narconon Arrowhead has been ruled accidental.
The cause of death is listed as "acute oxymorphone toxicity" an overdose of the drug oxymorphone.
Stacy Dawn Murphy of Owasso was found dead in July at the nonprofit drug and alcohol rehabilitation center in Pittsburg County.
Murphy's parents have filed a wrongful death lawsuit against the facility.
According to the petition filed in Pittsburg Co. District Court, the parents alleging wrongful death, negligence and violation of the Oklahoma Consumer Protection Act by Narconon Arrowhead are seeking more than $225,000 in damages.
Two other suits have been filed against Narconon. The mother of 32-year-old Gabriel Graves of Claremore filed in October and Hillary Holten's parents sued in August.