Michael Jackson, shown in November 2007, begged for the drug propofol to allow him to sleep, his doctor said. (Danny Moloshok/Associated Press)

A report by the Los Angeles coroner reveals there were lethal levels of the powerful anesthetic propofol in Michael Jackson's blood, according to a search warrant affidavit unsealed Monday in Houston, Texas.

The coroner is calling the pop star's death a homicide, a law enforcement official said Monday, speaking on condition of anonymity.

The coroner's report has still not been officially released, but the coroner determined Jackson died of a fatal combination of drugs, including propofol, on June 25, according to the official. Two other sedatives were also found in his blood.

The fact that the coroner considers the death a homicide makes it more likely criminal charges will be filed.

The Los Angeles Times reported that Jackson's doctor, Conrad Murray, who has a practice in Houston, admitted giving Jackson 25 milligrams of propofol just before his death.

Propofol is a powerful anesthetic administered intravenously in operating rooms to induce unconsciousness, and it is unusual to see it administered in a private home.

The star had demanded the drug to induce sleep, Murray told police, according to the affidavit.

He also told police he feared Jackson was forming an addiction to the drug and had tried to wean him off it over a period of weeks by giving him a lower dose and using other drugs.

The doctor told police he gave Jackson Valium at 1:30 a.m. and injected lorazepam intravenously at 2 a.m. on the day he died. When Jackson was still awake at 3 a.m. on June 25, Murray administered midazolam.

Then at 10:40 a.m., Murray administered 25 milligrams of propofol after Jackson begged for the drug.

Murray told police he left Jackson alone so he could make telephone calls to his Houston office and family members. When he returned, he discovered Jackson was not breathing and performed CPR.

Jackson was pronounced dead in hospital shortly afterward.

Murray's lawyer, Edward Chernoff, said in a statement late Monday his client never told detectives he left Jackson and returned to find he had stopped breathing on June 25.

Police detectives saw about eight bottles of propofol in Jackson's home, but also other drugs for inducing sleep such as Valium, lorazepam, temazepam, clonazepam, trazodone and tizanidine.

Police said they could find no evidence that Murray had purchased, ordered or obtained the propofol, according to the search warrant affidavit.

In addition to Murray, the singer had prescriptions from doctors Arnold Klein and Allan Metzger and from physicians in Germany.

With files from The Associated Press