A second post mortem examination is expected to be carried out on the body of Michael Jackson following a request from the singer's family.
As the world mourned the passing of the 50-year-old 'King of Pop', police and coroner's officials focused their investigations on the role prescription drugs may have played.
View a gallery of Michael Jackson's life
The results of the post mortem examination were deferred, possibly for between four and six weeks, and attention turned to Mr Jackson's doctor, who was with him when he fell ill.
Dr Conrad Murray, a cardiologist who practices in California, Nevada and Texas, will now be questioned further by detectives and his car was seized from outside Mr Jackson's house in case it contained drugs or other evidence.
Charlie Beck, assistant police chief of the Los Angeles Police Department, said it was 'way too early' to draw any conclusions about the singer's death.
He said officers spoke to Dr Murray immediately after Mr Jackson's death but now wanted to carry out 'an extensive follow-up interview'.
Craig Harvey, operations chief of the Los Angeles County Coroner's office, said there was no evidence of foul play or trauma on the superstar's body but further tests were needed.
He said he could not comment on any specific drugs that Mr Jackson may have been prescribed, but added: 'We know he was taking some prescription medications.'
He said: 'There was no indication of any external trauma or any indication of foul play on the body of Mr Jackson.'
The post-mortem examination took about three hours and Mr Jackson's body has now been released to his family.
Later, a source close to the investigation said Mr Jackson appeared to have suffered a heart attack.
A heart attack would not rule out drugs playing a role in his death, but could also indicate a long-term problem such as heart disease.
Mr Jackson, described by many as a misunderstood genius and one of the greatest performers of all time, died suddenly on Thursday, sending the world into mourning.
Among those leading the tributes to Mr Jackson was his close friend Dame Elizabeth Taylor who said: 'My heart... my mind... are broken.
'I loved Michael with all my soul and I can't imagine life without him.'
