Pop star Michael Jackson is shown Nov. 8, 2007. Police investigating his death said in warrants he might be considered an addict. (Associated Press)Los Angeles police detectives and federal drug agents were looking for evidence of a powerful anesthetic that may have played a role in Michael Jackson's death when they searched his doctor's house earlier this week.

Search warrants released Thursday show they were proceeding under the assumption that Jackson was an "addict" and been prescribed drugs under several different names.

Drug enforcement authorities searched Dr. Conrad Murray's home in Las Vegas, as well as his office and a storage unit in Houston.

Although they have never called Murray a suspect, they were seeking evidence for potential charges that might include excessive prescribing, prescribing to an addict, unprofessional conduct and manslaughter, all offences under California law.

The California Business and Professions codes related to practising physicians says they cannot prescribe drugs to anyone with a chemical dependency or who is using the drugs for non-therapeutic purposes.

An addict is defined as someone who continues to use a drug despite harm, shows compulsive use or has impaired control over use.

Jackson had been using prescription drugs as a sleep aid for years and had received anesthetics for various medical procedures.

His cause of death has not yet been determined and toxicology test results have been delayed.

However police detectives said earlier that they suspected the use of propofol, an anesthetic commonly used for surgeries, may have contributed to his death.

The warrants show agents were looking for documentation relating to the "purchase, transfer, receiving, ordering, delivery and storage of propofol."

In Las Vegas, the warrants said they were also looking for prescriptions issued under the names Omar Arnold, Josephine Baker, Paul Farance, Jack London and Michael Amir Williams Muhammad, which were among 19 aliases Jackson may have used.

Dr. Conrad Murray, shown in July 2006, owed hundreds of thousands of dollars in unpaid debts and had several financial judgments against him. (Houston Chronicle/Associated Press)Evidence from Murray's Las Vegas home showed he was in financial difficulty and may have jumped at the chance to earn $150,000 US a month to take care of Jackson during his London concert tour.

The Las Vegas cardiologist owed at least $780,000 US for settlements against his business, outstanding mortgage payments on his house, delinquent student loans, child support and credit cards.

Murray was under court orders to pay more than $363,000 US for equipment for his heart clinic and $71,000 US in student loans dating to the 1980s, a judgment that took effect in April.

He is also facing several lawsuits related to unpaid bills in Nevada courts and the mortgage on his $1.6-million US home was in arrears.

Murray, 56, has not spoken publicly since Jackson's June 25 death, but has been working with police, his attorney said.

With files from The Associated Press