The drug was just one of many among the pharmacopeia found in his Holmby Hills home. Officials have previously said that they believe the star was addicted to a daily dose of the pain medications OxyContin and Demerol and that Jackson was injected with Demerol shortly before his death June 25.
The medications found in his home included ones prescribed by multiple doctors to multiple patient names, some believed to be aliases, the sources told ABC News. The use of an alias may not be a crime, federal authorities said at this early stage of the investigation.
The finding appears to confirm reports by those close to Jackson, 50, that the singer had been abusing prescription drugs. On July 1, Los Angeles registered nurse and nutritionist Cherilyn Lee, who worked for Michael Jackson, came forward to saythe pop star begged her to help him obtain the drug in the days before he died.
The drug -- also known by the brand name Diprivan -- is most often used to sedate patients before a medical procedure, but it is also one that palliative care workers have been known to administer to terminal patients who are in pain or who have weeks or days to live.
Lee said during a call from a Jackson staffer, she heard Jackson in the background requesting the sedative.
"He said, 'Find me an anesthesiologist. I don't care how much money they want. find me an anesthesiologist to be with me here overnight and give me this IV,'" she said.
Jackson, Lee said, said he was in extreme discomfort, was desperate for sleep and said that one side of his body was hot and the other side cold.
Lee said she wasn't familiar with the drug when he first asked for it three months ago but after consulting with a doctor, warned Jackson it could kill him.
"'I look at you Michael and I've been around you long enough now, I love you as family. I would not give this to anyone,'" Lee said she told Jackson. "I said, 'This is not a safe medicine, please don't take this.'"
Pain specialists told ABC News that home use of the risky drug would be highly unusual, since it's ordinarily given in a hospital setting due to its health risks. Obtaining propofol with a simple prescription is next to impossible.
"Propofol has no place in a household," said Dr. Lloyd Saberski, a Yale University anesthesiologist and editor in chief of the journal The Pain Clinic. "This alone is a deviation, and many laws were likely violated just to get the propofol there."
Moreover, an injection of the drug requires that someone be present to continually administer it intravenously, said Dr. Howard Nearman, chairman of the anesthesiology department at University Hospitals Case Medical Center in Cleveland.
Nearman said there "absolutely" had to be a second party with Jackson if indeed he was using the drug to sleep.
Whether or not propofol was in Jackson's system at the time of his death will only be answered with the release of the pop star's autopsy results, which the Los Angeles County coroner's office has said will take weeks.
The potency of Propofol as an anesthetic is widely known; in anesthesiology circles, the drug, a white liquid, is termed "milk of amnesia" by some.