As grief for the King of Pop poured out around the world, from the icons of music to heartbroken fans, an autopsy showed no sign of trauma to Mr. Jackson, whose death came just weeks before he was to launch an epic comeback bid in a series of 50 concerts in London.
The person, who was not authorized to speak publicly
and requested anonymity, said Mr. Jackson had suffered a heart attack. Mr. Jackson's brother Jermaine had said the pop singer apparently went into cardiac arrest -- which often but not always happens because of a heart attack.
Authorities said they wanted to speak with the doctor, identified by the Los Angeles Times as cardiologist Conrad Murray, and said they had towed his car from Mr. Jackson's rented mansion because it could contain medication or other evidence. Police stressed that the doctor was not a criminal suspect.
Craig Harvey, a spokesman for the Los Angeles County coroner, said there were no signs of foul play. He said Mr. Jackson was taking some unspecified prescription medication but gave few details.
A 911 call released by fire officials shed light on the desperate effort at the mansion to save Mr. Jackson's life before paramedics arrived Thursday afternoon. Mr. Jackson died later at UCLA Medical Center.
In the recording, an unidentified caller pleads with authorities to send help, offering no clues about why Mr. Jackson was stricken. He tells a dispatcher that Mr. Jackson's doctor is performing CPR.
"He's pumping his chest," the caller says, "but he's not responding to anything."
Asked by the dispatcher whether anyone saw what happened, the caller answers: "No, just the doctor, sir. The doctor has been the only one there."
The autopsy was completed in a matter of hours, but an official cause of death could take up to six weeks while medical examiners await toxicology tests. No funeral plans had been made public.
Mr. Jackson had remained out of the public spotlight during intense rehearsals for the London concerts. Lou Ferrigno, the star of The Incredible Hulk , said he had been working out with Mr. Jackson for the past several months.
Still, Mr. Jackson's health had been known to be precarious in recent years, and one family friend said Friday that he had warned the entertainer's family about his use of painkillers.
"I said one day we're going to have this experience. And when Anna Nicole Smith passed away, I said we cannot have this kind of thing with Michael Jackson," Brian Oxman, a former Jackson attorney and family friend, told NBC's Today show.
Mr. Oxman claimed Mr. Jackson had prescription drugs at his disposal to help with pain suffered when he broke his leg after he fell off a stage and for broken vertebrae in his back.
The worldwide wave of mourning for Mr. Jackson continued unabated for the man who revolutionized pop music and moonwalked his way into entertainment legend.
"My heart, my mind are broken," said Elizabeth Taylor, who was one of Mr. Jackson's closest friends.
His two ex-wives both said they were devastated. One of them, Lisa Marie Presley, posted a long, emotional statement on her MySpace page in which she said her ex-husband had confided to her 14 years ago that he feared dying young and under tragic circumstances, just as her father, Elvis Presley, had.
"I promptly tried to deter him from the idea, at which point he just shrugged his shoulders and nodded almost matter of fact as if to let me know, he knew what he knew and that was kind of that," Ms. Presley said.