Hollywood actor Matthew Perry, best known for his starring role in the hit sitcom "Friends," died in October 2023 of what was determined to be an accidental overdose of a powerful anesthetic drug known as ketamine.

A criminal investigation has now been launched to uncover how and from where the deceased actor obtained the lethal dose of the drug, according to ABC News.

The probe is being led by the Los Angeles Police Department with federal assistance provided by the U.S. Drug Enforcement Agency and the U.S. Postal Inspection Service, per an email confirmation from LAPD Capt. Scot Williams.

Law enforcement probing origin and provision of drug to Perry

Celebrity gossip site TMZ was the first to report that, according to its law enforcement sources, the LAPD and the DEA were investigating the origins and circumstances of delivery of the ketamine drug that resulted in Perry's death.

That investigation has reportedly been ongoing for several months now and has involved multiple interviews with "key people in Hollywood" who are "known to have a history of drug use or abuse," though no arrests have been made to date.

The sources indicated that those people aren't necessarily suspected of being the actual source of the powerful drug, though it is believed that they may be able to provide information that will help investigators identify the source.

TMZ had also been the first to report that Perry had been found unresponsive in a hot tub at his Pacific Palisades home on October 28, 2023, and was declared dead at the scene by paramedics.

Perry's death ruled an accidental overdose of ketamine

It was initially suspected that Perry had drowned in his hot tub, but drowning was just one of several "contributing factors" to his death -- others included coronary artery disease and the effects of an opioid abuse treatment drug known as buprenorphine -- according to a December 15, 2023 report from the L.A. County Medical Examiner.

The primary cause of death, which was ruled an accident, was determined to be the "acute effects of ketamine."

According to Time magazine, ketamine is a "dissociative anesthetic with hallucinogenic properties" that has both medicinal and recreational uses, including for the treatment of depression and other mental health issues.

Perry was reportedly using an experimental treatment of the drug for his depression, known as ketamine infusion therapy, and had received a treatment roughly a week and a half before his death.

However, that relatively small treatment dosage would have been metabolized by his system quickly -- as soon as a few hours, per ABC News -- and the autopsy determined that Perry had a high level of ketamine in his system that was equivalent to the amount used in general anesthesia for surgery.

Other celebrity overdose deaths have been similarly investigated

Both ABC News and TMZ noted that it is not unheard of for law enforcement to investigate the origins and provision of lethal drugs in overdose cases involving deceased celebrities.

Some well-known examples include the 2018 death of rapper Mac Miller from fentanyl, the 2007 death of model Anna Nicole Smith from prescription drugs, and the 2009 death of singer Michael Jackson from the powerful anesthesia drug propofol.