Matthew Perry’s death is being investigated in connection with the level of ketamine in the actor’s blood

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

An assistant found Perry, 54, face down in his hot tub on Oct. 28 and paramedics who were called pronounced him dead immediately. His autopsy, released in December, found that the amount of ketamine in his blood was in the range needed to provide general anesthesia during surgery. It was listed as the primary cause of death, which was an accident with no suspected foul play, the report said.

Drowning and other medical problems contributed, the coroner said.

The investigation was first reported by TMZ.

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

But the medical examiner said Perry’s last treatment a week and a half ago would not explain the level of ketamine in his blood. The drug is normally metabolized within a few hours. At least two doctors treated Perry, 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 had years of addiction problems dating back to his time on “Friends,” when he became one of the biggest television stars of his generation as Chandler Bing alongside Jennifer Aniston, Courteney Cox, Lisa Kudrow, Matt LeBlanc and David Schwimmer for ten seasons from 1994 to In 2004 on NBC’s mega-hit sitcom.

In other cases, drug-related deaths of celebrities have led authorities to prosecute the people who supplied them.

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

Two doctors and a manager for model and reality TV star Anna Nicole Smith have been indicted for conspiring to get her prescription drugs before her death in 2007. However, they were not charged with causing a fatal overdose. All charges except one count of defrauding a doctor were ultimately dismissed.

And after Michael Jackson died in 2009 from a lethal dose of propofol – a drug intended only for surgery and other medical procedures, not for the insomnia the singer sought – his doctor Conrad Murray was convicted of manslaughter in 2011. Murray has maintained his innocence to this day.