The Canadian-born actor was found in his room at the Fairmont Pacific Rim Hotel around noon Saturday after he failed to check out. He'd been dead for several hours, and there was no evidence of foul play, authorities said.
"We do not have a great deal of information as to cause of death," British Columbia Chief Coroner Lisa Lapointe told Associated Press, saying further tests and investigation were needed. An autopsy was scheduled for Monday.
Video and electronic records from the hotel showed Monteith leaving with friends Friday night and returning alone early Saturday, acting Vancouver Police Chief Doug LePard told the AP. The actor is believed to have been alone when he died, he said. The friends who had been with him Friday night were being interviewed.
Monteith was dating 26-year-old costar
Monteith's last appearance on "Glee" was in the episode "Sweet Dreams," which saw his character at college and aired April 18.
"We are deeply saddened by this tragic news," Fox said in a statement. "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."
"At this time, please send nothing but love and light," tweeted costar
"OMG!! My Cory...,"
Dot-Marie Jones, who plays Coach Bieste, used all caps for emphasis, though we won't repeat them here:"I have no words! My heart is broken Cory was not only a hell of a friend he was one amazing men that I will hold close to my heart forever," she wrote. "I am blessed to have worked with him and love him so much! My heart is with hid family and our whole Glee family! I love you all!
Associated Press contributed to this report.