The Associated Press, citing a law enforcement official who spoke only on condition of anonymity, is reporting Jackson regularly received the anesthetic propofol. According to the official, a doctor would administer the drug when Jackson went to sleep, and would stop the IV drip when it was time to wake him up.

It is thought Jackson had been using propofol as a sleep aid for at least two years.

The unnamed official also said the police are working under the theory that a dose of propofol administered through an IV during the first few hours of June 25 by Jackson’s physician, Dr. Conrad Murray, killed the pop star.

This contradicts an earlier statement by Murray’s lawyer, Edward Chernoff, which claimed Murray “didn’t prescribe or administer anything that should have killed Michael Jackson.”

On Monday when Chernoff was asked about the unnamed law enforcement official’s statements, the lawyer responded: “We will not be commenting on rumors, innuendo or unnamed sources.”

Chernoff later posted online an addition to yesterday’s statement, saying “things tend to shake out when all the facts are made known, and I’m sure that will happen here as well.”

Murray, who became Jackson’s personal physician last May, is identified in court papers as the subject of a manslaughter investigation. Last week authorities raided his office and a storage unit in Houston.

Murray had been staying with Jackson at the rented mansion where the performer was living at the time of his death, and was supposed to accompany him to London when the artist began his round of shows at the O2 Arena. Chernoff claims he “happened to find” Jackson unconscious in the star’s bedroom on the morning of June 25 and tried to revive him by supporting his back with one hand while pressing on his chest with the other.

Meanwhile, Fox News, quoting yet another unnamed law enforcement official, is reporting Los Angeles police, Las Vegas police and DEA agents served a search warrant on Murray’s Las Vegas home. Last week officials interviewed doctors and personnel at Las Vegas medical facilities in an attempt to learn more about what caused Jackson’s death.

Click here for the complete Associated Press report.

Click here for the complete Fox News report.