Multiple people have been charged in connection with the accidental overdose death of actor Matthew Perry, law enforcement sources told NBC News on Thursday.

Perry, 54, was found face down in the heated end of a pool at his Pacific Palisades home on Oct. 28, 2023. The Los Angeles County Medical Examiner’s Office attributed his death to the acute effects of ketamine, an anesthetic with psychedelic properties.

At least one person was arrested in Southern California early Thursday, the sources said. Federal prosecutors are expected to unseal an indictment later in the day detailing the allegations against that individual and the others.

Los Angeles police said in May that they were working with federal authorities to investigate the source of the ketamine Perry had consumed.

Ketamine has been a popular party drug for decades. In recent years, it has shown promise as an alternative treatment for depression. A growing number of clinics offer it as an infusion or injection for a wide variety of mental health problems.

Perry had been undergoing ketamine infusion therapy to treat depression and anxiety, but his last session took place more than a week prior to his death. The medical examiner noted that the ketamine in Perry’s system “could not be from that infusion therapy” given its short half-life.