George Michael’s initial autopsy has been “inconclusive,” police said Friday, and further tests will be carried out to figure out his cause of death.

According to a statement released to the media by the Thames Valley police, “The cause of death is inconclusive and further tests will now be carried out. The results of the tests are unlikely to be known for several weeks.”

Michael’s death on Christmas Day is being treated as “unexplained but not suspicious.”

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The British singer-songwriter, best known for his successful solo career after breaking through as half of the pop duo Wham!, died at age 53 on Dec. 25.

“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,” said Michael’s rep in a statement to the BBC. “The family would ask that their privacy be respected at this difficult and emotional time. There will be no further comment at this stage.”

Michael died of heart failure, according to his longtime manager Michael Lippman.

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Michael, who was born Georgios Kyriacos Panayiotou to a Greek Cypriot restaurateur and his wife, first emerged as a hit-maker with Andrew Ridgeley in the pop duo Wham! in the early 1980s. Their early hits included the songs “Wake Me Up Before You Go-Go,” “Careless Whisper” and “Last Christmas.”

But he became a true pop icon after going solo in 1987, when his album “Faith” sold more than 20 million copies worldwide. In the span of his career, Michael sold more than 100 million records worldwide.

Michael won two Grammys among eight nominations and earned many other honors during his career, which spanned more than three decades.