Michael Jackson's mother claims the star may have been left to die.

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Katherine Jackson - who was devastated after the 'Thriller' singer died last month from a suspected cardiac arrest - believes Michael's personal physician Dr. Conrad Murray was responsible for his death after giving him large amounts of the anaesthetic Propofol just before the pop legend went to bed.

She alleges the doctor fell asleep while pumping the powerful drug into Michael's body.

Katherine spoke about her fears to family friend, world famous plastic surgeon Dr. Steven Hoefflin, around the same time Murray's office was being raided by police looking for evidence "of the offence of manslaughter".

Hoefflin told Britain's The Sun newspaper: "My opinion is Dr. Murray could have fallen asleep on the night Michael died while the IV [intravenous] drip administering Propofol was in Michael's arm.

"It has been very difficult to discuss these details with Katherine because of her understandable anger and grief. Over the last few days I have been with the family when the police were present and obtaining their information from the family about Michael.

"The evidence - as it is mounting - is horrifying."

Hoefflin also said Katherine believes two doctors are responsible for Michael's death and eight more could have their medical licences reviewed over their treatment of him.

Katherine's husband Joe has previously spoken of his concerns over Murray's conduct on the night his son died.

He said: "One of the doctors may have left or gone to sleep or something."

Meanwhile, Michael's nutritionist Cherilyn Lee has been served with a subpoena for the singer's medical records, which are currently at Lee's office.

Lee - who treated Michael between January and April - has alleged the singer asked for Diprivan, a powerful anaesthetic administered via an intravenous drip, to help him sleep.

It has also been revealed a string of department workers at the Los Angeles Country coroner's office have been accused of accessing Michael's death certificate.

Chief Investigator Craig Harvey said the person investigating the cause of death is the only one who should view the certificate, but some staff members printed copies of the file before it became a public record.

The certificate, which is kept in a supervised computer system, has been looked at on over 300 separate occasions.