The release of Michael Jackson's autopsy results has been delayed until next week, Los Angeles County Coroner's assistant chief Ed Winter confirmed Wednesday.

The Los Angeles coroner's office had earlier said Jackson's eagerly anticipated autopsy report would be revealed by Friday as speculation mounted about the possible role of prescription drugs in the pop star's death.

However Winter said Wednesday the results would now be released next week when toxicology reports are complete.

The delay came as Winter confirmed the coroner's office had issued a fresh subpoena seeking medical records from the office of a Beverly Hills plastic surgeon, Lawrence Koplin.

"I served a subpoena about noon for medical records for Michael Jackson and the doctor is cooperating," Winter said.

On Tuesday, federal agents and police raided the Las Vegas home and office of Jackson's personal doctor, Conrad Murray, who has become the central figure into the superstar's sudden death last month.

Search warrants filed in the investigation have indicated police are studying possible manslaughter charges against Murray, who is reported to have administered Jackson, 50, with a potent anesthetic before his death.

Jackson died on June 25 at his rented home in Holmby Hills as he prepared to relaunch his career with a gruelling series of comeback concerts in London.