There was no sign of foul play in the death of Michael Jackson, coroners who completed a post-mortem on the singer's body have said.
But toxicology and other tests have been ordered, and the cause of the 50-year-old's death could take several weeks to determine.
Police also want to speak to Jackson's doctor who witnessed his collapse.
Jackson's body has been released to his family but no funeral details have been made public.
Seven hours after the post-mortem examination was completed, Jackson's family was allowed to claim his body, seemingly managing to elude the media crowd outside the coroner's office.
The body has been taken to an undisclosed location.
Announcing the results of a three-hour autopsy, Los Angeles County Coroners spokesman Craig Harvey said there had been no indication of any external trauma or foul play, but he said the cause of death had been deferred.
"It means that the medical examiner ordered additional testing such as toxicology and other studies," Mr Harvey said.
These would take between four to six weeks, he said.
"We know he was taking some prescription medication," Mr Harvey said, without specifying which.
Unconfirmed reports suggest the singer had been taking a daily dose of Demerol, a painkiller also widely known as pethidine.
Jackson, who had a history of health problems, collapsed at his Los Angeles home around midday on Thursday.
A recording of the telephone call made to emergency services has been released, in which the caller said Jackson was unconscious and had stopped breathing.
His personal doctor - who witnessed his collapse - was trying to revive him, the caller said.
The singer was pronounced dead two hours later at the UCLA medical centre. Jackson's brother, Jermaine, said he was believed to have suffered a cardiac arrest.
Former Jackson family lawyer Brian Oxman told US TV that he had been concerned about the star's use of pain relief medication.
He told ABC's Good Morning America programme that Jackson took prescription pain relief for injuries sustained earlier in his career.
"It caused him great pain. He just didn't like to feel such discomfort. He started taking pain medication. It became part of his life," he said.
A spokesman for the Los Angeles Police Department said investigators had briefly spoken to Jackson's personal doctor, named by US media as Dr Conrad Murray, but they wanted to speak to him again.
Police also said a car owned by a doctor had been towed away from Jackson's home.
A spokeswoman said the doctor was not under criminal investigation, but that the car could contain "medications or other evidence that may assist the coroner in determining the cause of death".
The star had been due to stage 50 concerts at the O2 arena in London, beginning on 13 July.
