Law enforcement sources investigating the tragic death of Matthew Perry are close to concluding their probe and believe that "multiple" individuals should face federal charges. Perry, best known for his role on "Friends," was found unresponsive in a hot tub at his Los Angeles home and later pronounced dead at the age of 54. A postmortem toxicology report revealed that Perry's death was caused by a combination of drowning, coronary artery disease, buprenorphine, and ketamine. The primary cause of death was determined to be the effects of ketamine, with the manner of death ruled accidental. The U.S. Attorney's Office will decide whether to pursue charges, with the possibility of the case being referred back to California prosecutors. The investigation, which began in May and involved collaboration between the Los Angeles Police Department, Drug Enforcement Administration, and U.S. postal inspectors, aimed to trace the origin of the ketamine found in Perry's system. The police department formally launched its investigation in December, shortly after the release of the medical examination report.