Michael Jackson’s death has been ruled a homicide, a US law enforcement official has said, in a move that could open the door to criminal charges.

The Associated Press reported that the unnamed official stated that the Los Angeles County Coroner had determined that the singer died after being given a lethal cocktail of pharmaceutical drugs.

It comes as court documents revealed that Jackson’s personal doctor Conrad Murray administered a powerful sedative of the type believed to have killed him just hours before the pop star collapsed.

The developments have raised the possibility of charges being filed against Dr Murray, who has already been named as the target of a manslaughter investigation.

The LA County Coroner refused to confirm or deny the report by the Associated Press.

Captain John Kades, of the coroner’s department, said: “We have not released any information on the Jackson case. We do not know where this information is coming from.”

Under US law, homicide could refer to murder or negligent or reckless manslaughter.

Reports that the coroner had decided in favour of a homicide ruling came as court documents confirmed that authorities believe a lethal dosage of propofol killed the 50-year-old singer.

It also revealed that Dr Murray told police that in the day’s before Jackson’s demise he had administered several drugs to Jackson to help him sleep. These included propofol, which he administered via an intravenous line.

But he feared that the singer was becoming addicted to the drug and halved his dosage from 50 milligrams a night to 25 milligrams.

The last time Dr Murray administered the medication was 10.40am on June 25 – just hours before Jackson’s heart stopped.