Death of Matthew Perry is being investigated in connection with ketamine levels in the actor’s blood

LOS ANGELES (AP) — Authorities have launched an investigation to determine how Matthew Perry obtained the amount of ketamine that killed him, police said Tuesday.

Los Angeles police are currently working with the Drug Enforcement Administration and the U.S. Postal Inspection Service to investigate why the 54-year-old “Friends” star had so much of the drug in his system, LAPD Captain Scot Williams said in an email.

An assistant found Perry, 54, face down in his hot tub on Oct. 28, and paramedics who were called to the scene pronounced him dead immediately. His autopsy, released in December, found the amount of ketamine in his blood was in the range used for general anesthesia in surgeries. Ketamine was listed as the primary cause of death, and it was determined to be an accident with no foul play suspected, the report said.

Drowning and other medical problems were contributing factors, the coroner said.

TMZ first reported on the investigation.

People close to the actor told the medical examiner that he had undergone ketamine infusion therapy. The decades-old drug has been used more and more frequently in recent years to treat depression, anxiety and pain.

However, the medical examiner said Perry’s last treatment 1 1/2 weeks ago would not explain the level of ketamine in his blood. The drug is normally cleared within a few hours. Perry was treated by at least two doctors, a psychiatrist and an anesthesiologist who acted as his primary care physician, the medical examiner’s report said. No illegal drugs or paraphernalia were found in his home.

Perry struggled with addiction for years, dating back to his time on Friends. He became one of the biggest television stars of his generation when he played Chandler Bing alongside Jennifer Aniston, Courteney Cox, Lisa Kudrow, Matt LeBlanc and David Schwimmer in ten seasons of NBC’s mega-hit sitcom from 1994 to 2004.

In other cases, drug-related deaths of celebrities have led authorities to prosecute drug traffickers.

After rapper Mac Miller died of an overdose of cocaine, alcohol and counterfeit oxycodone containing fentanyl, two of the men who supplied him with fentanyl were convicted of distributing the drug. One was sentenced to more than 17 years in a federal prison and the other to 10 years.

Two doctors and a manager for model and reality TV star Anna Nicole Smith were indicted on charges of conspiring to provide her with prescription drugs before her death in 2007. However, they were not charged with causing her fatal overdose. All charges except one count of fraud against a doctor were eventually dropped.

And after Michael Jackson died in 2009 from a lethal dose of propofol – a drug that was only intended to be used during operations and other medical procedures, but not to treat the insomnia the singer was seeking – his doctor, Conrad Murray, was convicted of manslaughter in 2011. Murray has maintained his innocence to this day.