Michael Jackson's family are understood to have asked for a second post-mortem on the star's body.

Coroner's officer Brian Elias said: "My understanding is that they have requested a second autopsy. But we have no way of confirming that.

"The body is in a mortuary and if they want to proceed with a separate autopsy, it is up to them."

The first official examination was completed on Friday and the body released to the family. However, the first post mortem failed to provide any quick answers on what may have killed the superstar singer.

Officials confirmed it revealed no obvious signs of foul play but said further tests would be required, which could take several weeks.

Speculation is now focusing on the 50-year-old's use of prescription drugs, amid reports he was injected with a narcotic painkiller shortly before collapsing.

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

"Those tests we anticipate will take an additional four to six weeks. There was no indication of any external trauma or indication of foul play to the body of Mr Jackson."

The superstar's body was released to his family and taken to an undisclosed location in a single, unescorted vehicle.

Jackson was in full cardiac arrest when paramedics arrived at his rented $100,000-a-month mansion in Los Angeles on Thursday, with his personal physician trying desperately to revive him.

The pop superstar was rushed to the nearby UCLA Medical Center, where he was pronounced dead without regaining consciousness.

Police say they want to question Jackson's personal medic, identified in local media reports as Houston-based cardiologist Dr Conrad Murray.

There has so far been no word from the Jamily family on funeral arrangements.

Celebrity website TMZ.com, which broke the news of the singer's death, has cited an interview with an unidentified "close member" of the Jackson family, reporting the entertainer was injected with Demerol about half an hour before he went into cardiac arrest.

The website said the family believed Jackson's death was caused by an overdose of the drug, a painkiller.

Detectives have searched Jackson's home and impounded Murray's car from the driveway, believing it may contain evidence.

© Independent Television News Limited 2009. All rights reserved.