Preliminary findings said there was no evidence of foul play or external physical injury to Jackson, officials said.
Jackson's body was returned to his family on Friday night.
Meanwhile, a lawyer for Conrad Murray, the doctor at Jackson's rented mansion in the Holmby Hills neighbourhood of Los Angeles when he collapsed, said the physician had agreed to answer questions from police detectives.
"Dr Murray intends to fully cooperate with investigators and law enforcement as they attempt to piece together what happened," Bill Stradley told the Reuters news agency in an interview.
"Contrary to what has been out there, Dr Murray has been co-operating with authorities from the outset and will continue to do so," Stradley said.
"The impression that he has been hiding from authorities, that's not correct."
Murray was desperately trying to revive Jackson when paramedics arrived and he rode with the singer in an ambulance to the hospital where the pop star was pronounced dead.
Police have said they wanted to further question Murray, a Houston-based cardiologist, about the circumstances of Jackson's death but had not been able to arrange an interview.
Murray's silver Mercedes was towed from the home where Jackson died so that detectives could search it for evidence and medication.
The Reverend Jesse Jackson, who has been acting as a spokesman for the singer's parents, told CNN that the family would "without a doubt" order an independent examination of the remains.
"This thing has gone from inquiry to investigation," Jesse Jackson told the CNN news channel.
"Right now there is no peace. We don't know what happened and we need to know. Michael was not sick before [Wednesday] night. He was not frail."
|Thousands of fans paid tribute near Jackson's star on the Hollywood Walk of Fame [AFP]
Speculation has centered on Jackson's use of prescription drugs and reports that he was injected with the narcotic painkiller Demerol shortly before he went into cardiac arrest.
Jesse Jackson told ABC News that his family also had questions for Murray.
"When did the doctor come? What did he do? Did he inject him? If so, with what?" he said in an interview with the network.
"Was he on the scene twice? Before and then reaction to? Did he use Demerol? It's a very powerful drug. Was he injected once? Was he injected twice?"
TMZ reported that police were also interested in speaking with another Jackson adviser, Tohme Tohme, about the superstar's use of prescription medication.
Coroner's officials have said that with no outward signs of trauma to Jackson's body or evidence of foul play, they would have to wait for the results of toxicology tests and other studies to establish a cause of death.
Few other details were released about the autopsy's findings, but Fox News reported on its website that investigators had found his body to be healthier and stronger than they had expected with some scarring on the face.
Facing a battered reputation and a mountain of debt that The Wall Street Journal reported ran to $500 million, Jackson spent the last two months of his life rehearsing for a series of London concerts that were seen as a make-or-break comeback for the man who dominated the pop charts in the 1980s.