Media reports about possible drug use by pop star Michael Jackson the day he died prompted a warning from anesthesiologists on Sunday, as lawyers prepared to square-off in a courtroom battle over his estate.

Reports of prescription drug use have increasingly surfaced since the Thriller singer's sudden cardiac arrest more than one week ago, and a police probe is said to be focusing on the role doctors may have played in providing Jackson with at least one powerful medication, anesthetic Diprivan, according to the Los Angeles Times.

Investigators are trying to determine if the drugs, which were found in searches of Jackson's rented Los Angeles mansion, were improperly prescribed and if they had a role in the June 25 death of the King of Pop at age 50.

Numerous bottles, of Diprivan without labels were found at the mansion, according to the Los Angeles Times.

Diprivan, the brand name of propofol, is an anesthetic that should never be used outside of a controlled and monitored medical setting, the American Society of Anesthesiologists (ASA) said in a statement, noting that its members have not studied the particulars of Jackson's death.

Patients can have extremely variable responses to the drug and some patients can become completely anesthetized, including losing the ability to breathe, the group said.

Two autopsies were performed on Jackson after his death but toxicology results are not expected for weeks.

BATTLE OVER JACKSON'S ESTATE

Meanwhile, the battle over Jackson's estate was set to move forward on Monday, with a hearing scheduled in Los Angeles Superior Court between lawyers for his 79-year-old mother, Katherine Jackson, and attorneys who were named as co-executors of a Jackson will that surfaced late last week.

At stake is a fortune that an attachment to the will estimated could be worth more than $500 million, although Jackson has been reported as deeply in debt the day he died.

Katherine Jackson was granted temporary administrator of Jackson's affairs last week before the will, which names lawyer John Branca and music executive John McClain, as co-executors over the 2002 will, putting his assets in a family trust that benefits his three children, Katherine Jackson, and charities.

A separate hearing over the guardianship of Michael Jackson's children has been postponed until July 13. In the meantime, Katherine Jackson has been named temporary guardian of Prince Michael Jackson Jr. 12, Paris Michael Katherine Jackson, 11, and Prince Michael Joseph Jackson, II, 7.

About 1.6 million people have registered to be one of 8,750 people who will get two free tickets to attend Jackson's public memorial, set for Tuesday morning in downtown Los Angeles.

Fans who are chosen will be e-mailed Sunday, organizers said.

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