The Los Angeles County coroner's office determined the cause of death was "acute propofol intoxication." Lorazepam, another sedative sold under the brand name Ativan, contributed to the death.
Additional drugs detected in Jackson's system were the sedatives midazolam and diazepam, the painkiller lidocaine and the stimulant ephedrine.
The coroner did not release Jackson's full autopsy report, citing a security hold requested by Los Angeles authorities investigating the case, and declined to comment beyond a short statement announcing the manner and cause of death.
"The findings are not a surprise but they do confirm that the singer had an awful lot of very strong medicine in his body when he died, a fact that clearly will help determine whether prosecutors now believe they have enough physical evidence to charge someone, including Jackson's treating physician Conrad Murray, with some sort of involuntary manslaughter charge," says CBS News legal analyst Andrew Cohen.
"The key here is not to get caught up in the use of the word 'homicide.' It does not mean we are going to see an intentional murder case here," Cohen notes. "It's just a generic word the medical examiner uses. When the prosecutor's office starts talking about terms like that we'll need to pay attention and I still think the most likely scenario here is an involuntary manslaughter charge against someone."
The coroner's determination of a homicide confirmed what The Associated Press first reported Monday, citing an anonymous law enforcement official.
The 50-year-old Jackson died June 25 at his rented Los Angeles mansion. Dr. Conrad Murray, the Las Vegas cardiologist who was the pop star's personal physician, told police he gave Jackson propofol that morning after a series of sedatives failed to help Jackson sleep.
Murray has not been charged with any crime but is the target of what police term a manslaughter investigation. Multiple search warrants served at his home and businesses in Las Vegas and Houston sought evidence detailing how he procured the propofol that killed Jackson. Jackson's interactions with at least six other doctors also are being scrutinized.
Except for a brief video posted to YouTube earlier this month, Murray has not spoken publicly since Jackson's death. In the video, he said: "I told the truth and I have faith the truth will prevail."
Murray's attorney, Edward Chernoff, said he was disappointed the full autopsy report wasn't released. Without that, it was impossible to seek independent expert opinion on the significance of the various drugs detected.
"Release the toxicology report, the whole thing. Sunlight is the best disinfectant," Chernoff said. "This smells like gamesmanship."
Chernoff repeated his assertion that nothing Murray gave Jackson "should have" killed him.
It's not clear when the full report may be released. The coroner said the security hold would remain until the investigation is wrapped up. The Los Angeles Police Department and the district attorney's office said they did not know when that would be.
A statement by the LAPD said the investigation into the death is ongoing and "will result in the case being presented to the Los Angeles County District Attorney for filing consideration."
The coroner's determination of homicide makes it more likely criminal charges will be filed but does not guarantee it. In the past seven years just a handful of doctors have been convicted of manslaughter, mostly involving their patients' use of painkillers. To win a conviction, prosecutors would have to show that Murray acted recklessly and with negligence.
Murray was hired by Jackson's promoter AEG Live to help keep the aging star fit during the grueling preparation for a series of comeback "This Is It" concerts in London. Jackson got to know Murray in Las Vegas, where he moved after a stint overseas following his 2005 exoneration on child molestation charges and where the Caribbean native ran a clinic.
It was a break and a $150,000-a-month salary that Murray desperately needed. The doctor hadn't paid the mortgage on his country club mansion in 2009, and according to court records he owed a total of at least $680,000 in judgments against him and his medical practice, delinquent student loans, child support and credit cards.
Murray has been interviewed twice by police. According to court records, he told investigators that over about six hours he injected Jackson with two doses each of lorazepam and midazolam. Finally, around 10:40 a.m., Murray said he succumbed to Jackson's demands and administered propofol, a drug Murray said he had given Jackson every night for six weeks. He said he had diluted the propofol with lidocaine.
Propofol, dubbed "milk of amnesia" among anesthesia professionals, commonly is used to render patients unconscious for surgery. It's only supposed to be administered by anesthesia professionals in medical settings and, because of its potency, requires the patient be closely monitored at all times. Using propofol strictly as a sleep agent violates medical guidelines.
Medical experts said the drugs found in Jackson's system magnify each other's effects.
"Instead of one plus one equals two, one plus one equals three," said Lee Cantrell, a toxicologist and director of the San Francisco division of the California Poison Control System.
A search warrant affidavit unsealed this week in Houston includes a detailed account of what detectives say Murray told them. The doctor said he'd been treating Jackson for insomnia for about six weeks with 50 milligrams of propofol every night via an intravenous drip, the affidavit said. Murray said he feared Jackson was becoming addicted to the anesthetic, which is supposed to be used only in hospitals and other advanced medical settings, so he had lowered the dose to 25 milligrams and added the sedatives lorazepam and midazolam.
That dosage is very small and by itself it's very unlikely it would have killed him. But with the other drugs there was a "benzodiazepine effect," according to the coroner, and it was deadly.
Dr. David Zvara, anesthesia chairman at the University of North Carolina at Chapel Hill, said it's difficult to determine what constitutes a fatal dose of propofol in someone receiving other sedatives.
"It's hard to set any level because of the way those act in synergy," he said. Given after the sedative lorazepam, "Even a small dose of propofol might have a very large effect."
Jackson had many medical procedures over the year and a long history with various drugs. Following his death, three medical professionals said Jackson asked them for propofol this spring. All refused. One, a registered nurse named Cherilyn Lee, recounted that Jackson told her he liked how the drug knocked him out fast and allowed him to sleep for hours longer than he could naturally.
Doctors were surprised by the coroner's mention of ephedrine, once sold as the controversial diet drug Ephedra and now banned by the federal Food and Drug Administration, though the drug can be used for resuscitation. Zvara said it's unlikely emergency personnel who responded to Jackson's home would have used that drug since epinephrine, otherwise known as adrenaline, is favored.