The coroner's office is investigating an outpatient death at the Montreal General Hospital.
A 65-year-old man was found in a closed-clinic area of the building on Sunday morning.
He was unconscious and efforts to revive him failed.
The man went missing after receiving scheduled treatment Saturday night at the hospital.
McGill University Health Centre officials say they aren't permitted to divulge details about the care he received.
CTV Montreal has learned that he was suffering from mental illness, but the treatment was for a separate physical ailment.
The hospital would not confirm reports that it was the man's taxi driver who alerted hospital staff that the he had not taken his ride home.
