The 50-year-old singer was pronounced dead after being taken to hospital in in a deep coma.
Jackson's brother Jermaine said it was believed he suffered a cardiac arrest in his home in Holmby Hills.
"My brother, the legendary King of Pop, passed away on Thursday, June 25, at 2.26pm.
"We believe he suffered a cardiac arrest at his home, however the cause of his death is unknown until the results of the autopsy are known.
"His personal physician, who was with him at the time, attempted to resuscitate my brother, as did the paramedics who transported him to UCLA Medical Centre in Los Angeles.
"On arrival at 1.14pm a team of doctors including emergency physicians and cardiologists attempted to resuscitate him for one hour but they were unsuccessful."
Jackson was pronounced dead at about 1426 local time (2226 British time).
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