Doctors completed an autopsy on the body of Michael Jackson on Friday but said they could not immediately establish a cause of death for the "King of Pop" as speculation centered on his use of prescription painkillers.

"The cause of death has been deferred, which means that the medical examiner has ordered additional testing such as toxicology and other studies," Los Angeles County Coroner's spokesman Craig Harvey said.

"Those tests we anticipate will take an additional four to six weeks."

Speaking to a throng of reporters outside the coroner's office, Harvey said, "There was no indication of any external trauma or indication of foul play to the body of Mr. Jackson."

He said his office expected to determine what killed Jackson, 50, when the tests were complete.

The body would be released to family members after they chose a mortuary to handle the funeral arrangements, Harvey added.

Celebrity Web site TMZ.com, citing an interview with an unidentified "close member" of the Jackson family, reported the superstar singer was injected with Demerol about half an hour before he went into cardiac arrest.

Police searched Jackson's rented mansion in the Holmby Hills neighborhood of Los Angeles and planned to interview his personal physician, who was with the entertainer at the time of his death.

TMZ, citing family members, said Jackson received a daily injection of Demerol, a narcotic painkiller. The family believes his death was caused by an overdose of the drug, TMZ reported.

An unidentified man called a 911 emergency phone line from the mansion at 12:21 p.m. local time, saying Jackson was unconscious and not breathing.

In excerpts from the call played on television, the man said the doctor was the only other person present and was performing cardiopulmonary resuscitation on the unconscious Jackson without results.

"He's pumping, he's pumping his chest but he's not responding to anything, sir, please," the caller said.

A senior law enforcement official told ABC News that Jackson was "heavily addicted" to the painkiller Oxycontin and was injected daily with that medication, along with Demerol.

Lawyer Brian Oxman, a Jackson family spokesman, told CBS' "The Early Show" he had been concerned about the prescription drugs Jackson took due to injuries suffered while performing.

"I do not want to point fingers at anyone because I want to hear what the toxicology report says and the coroner says but the plain fact of the matter is that Michael Jackson had prescription drugs at his disposal at all times," Oxman said.

Fans and fellow pop stars everywhere revived memories of Jackson's musical genius, tarnished over the past decade by accusations of child molestation and eccentric behavior.

U.S. President Barack Obama called Jackson a "spectacular performer" but said he believed aspects of his life were "sad and tragic," the White House said.

Jackson's death was front-page news around the world as airwaves filled with his greatest hits from "Thriller" to "Billie Jean" and social networking sites were bombarded with messages and tributes.

"My heart, my mind are broken," actress Elizabeth Taylor, long a close friend of Jackson, said in a statement.

"He will be in my heart forever but it's not enough," Taylor said. "My life feels so empty. I don't think anyone knew how much we loved each other."

On Hollywood Boulevard, police put up barricades to control thousands of fans who filed past Jackson's star on the Walk of Fame to honor the child prodigy who became one of the top singers of all time with an estimated 750 million albums sold.

Jackson's family has yet to announce details of a funeral.

Facing a battered reputation and a mountain of debt that The Wall Street Journal reported ran to e500 million, Jackson spent the last two months rehearsing for a series of London concerts, including Wednesday in Los Angeles.

Despite reports of Jackson's ill health, the promoters of the London shows, AEG Live, said in March that Jackson passed a 4 1/2-hour physical examination with independent doctors.

In death, Jackson's music enjoyed an immediate rebound that eluded him for years. His songs surged to the top 15 on online retailer Amazon.com's best-selling albums within hours.

He dominated the charts in the 1980s and was one of the most successful entertainers, with 13 Grammy Awards and several seminal music videos. His 1982 album "Thriller" yielded seven top-10 singles.

But he was twice accused of molesting young boys and was charged in 2003 with child sexual abuse. He was acquitted of all charges in a four-month trial in 2005.

In 1994, Jackson married Elvis Presley's only child, Lisa Marie, which ended in divorce in 1996. He remarried and had two children, later split with his second wife, and had a third child with an unnamed surrogate mother.