The president of the company promoting Jackson's shows said Murray was Jackson's personal physician for three years. Jackson insisted Murray accompany him to London, said Randy Phillips, president of AEG Live.

Phillips quoted Jackson as saying: "Look, this whole business revolves around me. I'm a machine, and we have to keep the machine well-oiled." Phillips said Jackson submitted to at least five hours of physicals that insurers had insisted on.

On Friday, 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.

Jackson had remained out of the public spotlight during intense rehearsals for the London concerts, but those with access said he was upbeat and seemingly energized by his planned comeback. Ken Ehrlich, executive producer of the Grammys, said he watched Jackson dance energetically as recently as Wednesday.

"There was this one moment, he was moving across the stage and he was doing these trademark Michael moves, and I know I got this big grin on my face, and I started thinking to myself, 'You know, it's been years since I've seen that,'" he said.

Lou Ferrigno, the star of "The Incredible Hulk," said he had been working out with Jackson for the past several months.

Still, 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. "The result was I warned everyone, and lo and behold, here we are. I don't know what caused his death. But I feared this day, and here we are."

Oxman claimed 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 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 Jackson's closest friends and married one of her husbands at a lavish wedding at the pop star's Neverland Ranch in 1991. She said she had heard the news as she was preparing to travel to London for Jackson's comeback show, and added, "I can't imagine life without him."