Police open investigation into ketamine which killed Friends star Matthew Perry

Matthew Perry, who was famous for his role as Chandler Bing in Friends, died in October last year.

A post-mortem revealed his death was an accident from "the acute effects of ketamine" - which is used a recreational drug and to treat depression.

Now it's been reported the Los Angeles Police Department have opened an investigation into why there was so much ketamine in the actor's system. According to his autopsy, Matthew was undergoing ketamine infusion therapy.

Matthew's last treatment was one and a half weeks before his death - but the medical examiner said it would not explain the levels of ketamine in his blood. The examiner added he also also drowned in the "heated end of his pool" - which was a secondary factor in his death.

The news comes after Matthew's co-star Courteney Cox said the late actor "visits me a lot". Speaking about the 20th anniversary of Friends on CBS Sunday Morning, she said: "You know, he’s just so funny.

"He has genuinely a huge heart, obviously struggled. I’m so thankful I got to work so closely with him for so many years. He visits me a lot, if we believe in that.”

When asked about her spirituality, the actress added" "You know, I talk to my mom, my dad, Matthew — I feel like there are a lotta people that, I think, guide us. I do sense, yeah, I sense Matthew’s around for sure.”

At the time of Matthew's death, the cast of Friends paid tribute to the star and Courteney shared a personal tribute on her Instagram page. She wrote: "I am so grateful for every moment I had with you Matty and I miss you every day.

"When you work with someone as closely as I did with Matthew, there are thousands of moments I wish I could share. For now here’s one of my favorites. In this scene, before we started rolling, he whispered a funny line for me to say. He often did things like that. He was funny and he was kind."

The Friends cast are said to have decided not to make a big deal out of the show's anniversary due to Matthew's death. An insider shared: "The prospect of having a reunion or a formal get-together without Matthew is bittersweet. There will be a huge void. [But] they know Matthew would’ve wanted them to carry on and celebrate the show. So that’s very much on their minds as they move forward.”