Jackson's body was rushed to the UCLA medical centre where after failed attempts to resuscitate him he was pronounced dead two hours later.
Jermaine Jackson, brother of the singer, said that it is thought that Michael had died from heart failure.
Michael Jackson had been due to stage a return to performing by taking part in a series of concerts in the UK, that were due to start on 13 July.
Television footage showed Jackson's body being taken from the UCLA centre to the Los Angeles County Coroner's office where a post-mortem is thought to being conducted on Friday.
Only last month, there had been serious concerns about the singer's health because four of Jackson's planned UK concerts were postponed, but the organisers claimed the dates had been changed because of problems with staging the show.
Jackson had a history of health problems and it is now being speculated that his efforts in preparing for the forthcoming shows proved to much for him.
Jackson began his legendary career as a child member of The Jackson 5 pop group.
Tributes are pouring in worldwide from many of Jackson's friends in the business of entertainment and his millions of fans are in a state of severe shock and grief.
Jackson was the father of three children, Michael Joseph Jackson Jr, Paris Michael Katherine Jackson and Prince Michael Jackson II.
His mother, Katherine, father, Joseph as well as eight brothers and sisters - including Janet, Randy, Jermaine and La Toya Jackson - all survive him.
