5:45 PM PT -- Sources directly connected with George and in a position to know tell us the singer died from heart failure. We're told he was sleeping throughout the episode and suffered no pain.

4:15 PM PT -- One of Michael's principal reps tell TMZ the singer had not been ill, and had been working on a Showtime movie of his life that was set to air in England next March.

George Michael passed away at his home in England at the age of 53 … his rep confirms.

A rep for the pop star says, "It is with great sadness that we can confirm our beloved son, brother and friend George passed away peacefully at home over the Christmas period."

Details surrounding Michael's death have not been released.

Police say the death is unexplained, but doesn't appear to be suspicious, according to the BBC.

George was a music legend -- and sold more than 100 MILLION albums during his career.

Michael launched his career with WHAM! in the'80s -- churning out hits like "Wake Me Up Before You Go-Go" and "Careless Whisper."

He went on to have a monster solo career with hits like,"I Want Your Sex" and"Faith."

Michael struggled with drugs during his life -- and was arrested several times including an incident where he was busted at a public toilet in London in 2008.

Story developing.