Vancouver police and the British Columbia coroner say there appeared to be no signs of foul play, no apparent cause of death and that the 31-year-old actor had been dead for several hours.
Acting Vancouver Police Chief Doug LePard passed on his condolences to the family, friends, castmates and millions of Monteith's fans.
"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."
Monteith's body was found in his room on the 21st floor of the Fairmont Pacific Rim Hotel around noon local time on Saturday.
He checked into the room July 6 and was due to check out Saturday, LePard said.
"When he missed his check-out time, staff went to the room at noon and found his body."
LePard said investigators have spoken with some of the people Monteith was with Friday night, but added it appeared he was alone at the time of his death.
Chief Coroner Lisa Lapointe said further tests would be needed to determine how Monteith died.
``The exact nature of those examinations will depend on investigative findings within the next day or two as information is gathered from medical records and discussions with family take place,`` she said.
Best known for his role as Finn Hudson on the Fox television series "Glee," Monteith was born in Calgary and raised in Victoria, B.C.
Before becoming an actor, he worked in Nanaimo, B.C. as a Wal-Mart people greeter, taxicab driver, school bus driver, and roofer.
Monteith played minor roles in "Final Destination 3," "Whisper" and "Deck the Halls," and had a recurring role in "Kyle X."