Authorities have "uncovered an extensive criminal network" that they link to Matthew Perry's drug-related death.

Five people are accused, including two doctors and the actor's personal assistant.

Police said Thursday that their investigation, which began in May, had uncovered an "extensive underground criminal network" of drug suppliers who distributed large quantities of ketamine.

Perry, 54, died at his home in Los Angeles in October. A post-mortem examination revealed a high concentration of ketamine in his blood and determined that the "acute effects" of the controlled substance were the cause of his death. it says "with the BBC".

"These defendants took advantage of Perry's addiction problems to enrich themselves," said U.S. Attorney Martin Estrada, adding that they knew what they were doing posed a great danger to the actor, but they did it anyway.

Three of the defendants – including Perry's assistant – have already pleaded guilty to drug charges, while two others – a doctor and a woman known as the 'Ketamine Queen' – were arrested today.

Ketamine is a powerful anesthetic used as a treatment for depression, anxiety and pain.

People close to Perry, who starred as one of the main characters in the NBC television show Friends, told an inquest after his death that he had been receiving ketamine infusion therapy.

The levels of ketamine in his body were as high as the amount given during general anesthesia, doctors said.

The indictment filed in federal court detailed an elaborate drug-buying scheme that prosecutors say ultimately led to Perry's death.

Prosecutors said Perry's assistant, Kenneth Iwamasa, worked with two doctors to provide the actor with more than $50.000 worth of ketamine in the weeks before his death.

Officials alleged that those involved in the scheme sought to capitalize on Perry's well-known substance abuse problems.

One of the doctors, Salvador Plasencia, reportedly wrote in a text message: "I wonder how much this moron will pay."

Prosecutors say Perry's assistant paid a doctor thousands of dollars for the ketamine

Other defendants in the case include Jasven Sanga, the so-called "Queen of Ketamine," who supplied the drug to Placencia with the help of two other defendants, Eric Fleming and doctor Mark Chavez.

Prosecutors say the defendants tried to cover up their involvement in the crimes after Perry's death.

At the height of her fame, Perry struggled with addictions to painkillers and alcohol and visited rehab on multiple occasions. He described his struggle with substance use in his memoir.

In 2016, he told BBC Radio 2 that he could not remember three years of filming during Friends, due to alcohol and drugs.

After attempts at treatment, he wrote in his memoir that he had been mostly sober since 2001.