Glee star Cory Monteith has been found dead in a hotel room in Canada, Vancouver Police have confirmed.
The 31-year-old's body was discovered at Vancouver's Fairmont Pacific Rim hotel just after noon on Saturday after he failed to check out.
Police believe he was alone when he died, and have ruled out foul play.
Doug LePard, the acting chief of Vancouver Police, said: "As was the case in countless homes, I watched Glee regularly with my daughters, and I know there will be shock and sadness in many households with the news of his tragic death.
"Mr Monteith checked into the hotel on July 6 and was due to check out of the room (on Saturday).
"There were others with Mr Monteith in his room earlier ... but video and fob key entries show him returning to his room by himself in the early morning hours and we believe he was alone when he died."
Monteith had voluntarily entered rehab for substance abuse problems in April.
It was not Monteith's first time in rehab. He received treatment when he was 19 and had previously talked about his addiction struggles, saying he had a serious problem and took just "anything and everything".
He told Parade magazine in 2011 that he was "lucky to be alive".
He was best known for playing Finn Hudson in the popular musical comedy series Glee, which follows a group of American secondary school misfits.
A post-mortem will take place on Monday, and the coroner will decide on the next steps to establish the cause of death.
A statement on behalf of Glee's executive producers and 20th Century Fox Television said: "We are deeply saddened by this tragic news.
"Cory was an exceptional talent and an even more exceptional person. He was a true joy to work with and we will all miss him tremendously. Our thoughts and prayers are with his family and loved ones."
Stars have spoken of their shock at the news.
Dot-Marie Jones, who plays Coach Bieste in Glee, wrote on Twitter: "I have no words! My heart is broken, Cory was not only a hell of a friend, he was one amazing man that I will hold close to my heart forever."
Singer Taylor Swift wrote: "Speechless. And for the worst reason."
Actress Jaimie Alexander added: "Sweet man... Gone far too soon. Peace be with you friend."
Singer Lance Bass said: "Devastated about the news of Cory Monteith - such an incredible guy - my thoughts are with his family and friends."
And Zooey Deschanel wrote: "What an absolutely tragic loss of a very talented young man."