A spokesman for the Los Angeles county coroner says the cause of death of singer Michael Jackson cannot be determined until more testing has been completed, in four to six weeks. The pop superstar fell ill in his rented home Thursday, and was pronounced dead a short time later at a Los Angeles hospital. Friends and fans are paying tribute as they wait for word on the cause of Jackson's death at the age of 50.

Spokesman Craig Harvey says the Los Angeles coroner is deferring, or postponing, release of its findings "... which means that the medical examiner has ordered additional testing such as toxicology and other studies. Those tests, we anticipate, will take approximately four to six additional weeks."

He offered little information from preliminary findings of Friday's autopsy, beyond ruling out foul play. "There was no indication of any external trauma or any indication of foul play on the body of Mr. Jackson."

The spokesman did confirm that the singer was taking some prescription medications, but could not say whether they played a role in his death.

Police towed a car Friday from Jackson's rented home. It belonged to one of his doctors, and police said they were looking for medications that could be related to Jackson's death. Police say they want to talk to the doctor, who was with Jackson when he fell ill and unsuccessfully tried to resuscitate him.

Authorities also released the recording of the emergency phone call of an unidentified caller asking for medical help. He said the singer was on a bed and was unconscious.

"(CALLER) Sir, we have a gentleman here that needs help and he's not breathing. He's not breathing, and we're trying to pump him but he's not, he's not.

(EMERGENCY OPERATOR) OK. OK. How old is he?""

(CALLER) He's 50 years old, sir."

Michael Jackson was part of a family pop group, the Jackson 5, and he soared to international stardom as a solo performer.

Fans continued to offer tributes to the man called the King of Pop outside the singer's rented home and at the Jackson family compound in another part of the city. Many gathered by Jackson's star on the Walk of Fame on Hollywood Boulevard, and some went to Neverland Ranch, where the singer once entertained close friends and visiting youngsters. Jackson was accused of molesting a 13-year-old boy at the ranch in 2003, but was acquitted of the charges two years later.

Friends in the entertainment world have expressed their grief, with pop diva Diana Ross calling Jackson's death too sudden and shocking. A distraught Elizabeth Taylor issued a statement saying her life will be empty after the loss of her close friend.

Tributes from fans were offered cities from New York to London and Tokyo. A White House spokesman said President Obama viewed Michael Jackson as a spectacular performer but noted that his life had sad and tragic aspects. The U.S. House of Representatives observed a moment of silence.