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Investigators probing Michael Jackson's death looked for evidence related to the powerful anesthetic propofol when they searched his doctor's Las Vegas home and business, according to search warrants filed Thursday that alluded to the pop star being an "addict."

Los Angeles police and federal Drug Enforcement Administration agents spent much of the day Tuesday at Dr. Conrad Murray's properties looking for evidence supporting a manslaughter charge and various violations of the California Business and Professions Code, including "prescribing to an addict," "excessive prescribing" and "unprofessional conduct."

The code states a physician cannot prescribe drugs to anyone thought to have a chemical dependency or who is using the drugs for non-therapeutic purposes.

The warrants, which had been sealed when the searches were conducted, also said investigators wanted all documentation relating to the "purchase, transfer, receiving, ordering, delivery and storage of propofol."

A law enforcement official earlier told The Associated Press that on the day Jackson died Murray gave him propofol to help him sleep and that investigators are working under the theory the anesthetic caused Jackson's heart to stop. The official spoke on condition of anonymity because the investigation is ongoing.

A cause of death has yet to be announced. The Los Angeles County coroner has twice said toxicology findings on Jackson were imminent but after meeting Thursday with investigators assistant chief coroner Ed Winter announced an indefinite delay. Winter said further investigation needs to be done; he did not go into detail.

Propofol, dubbed "milk of amnesia," is commonly used for surgeries and is not meant as a sleep agent or to be given in private homes. Because of its potency, only trained anesthesia professionals are supposed to administer it and patients are to be monitored at all times.

Murray, a 56-year-old cardiologist, has spoken to police but not commented publicly since Jackson died June 25.

Murray's attorney, Edward Chernoff, did not immediately respond to a request for comment Thursday. He has previously said the doctor did not prescribe anything that "should have" killed Jackson.

Jackson was given anesthesia for numerous medical procedures over the years and had a long history of prescription drug use.

Search warrants issued last week in Houston allowed authorities to search Murray's clinic and a storage unit. They were the first public acknowledgment that investigators consider Jackson's death a possible manslaughter and that Murray is the target of the investigation.

The Las Vegas warrants were far more detailed and authorized authorities to look for medical and other records related to Jackson or any of the apparent 19 aliases he used, including the names Omar Arnold, Josephine Baker, Paul Farance, Jack London and Michael Amir Williams Muhammad.

Among the items seized in the Vegas searches were an iPhone, copies of several computer hard drives, a CD with the name Omar Arnold on it and a binder containing invoices for medical equipment and supplies. No propofol was found.

A warrant was also served at a storage locker, but no items were taken.