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.
Propofol Found in Jackson's Home a Potentially Deadly Drug
"'I look at you Michael and I've been around you long enough now, I love you asfamily. 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.
Propofol Known as 'Milk of Amnesia'
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.
"Propofol is an agent that requires very close monitoring and is often limited only to use by anesthesiologists," said Dr. Richard Page, head of cardiology at the University of Washington medical center. "The main issue with this agent is respiratory depression, which in turn could cause cardiac arrest."
"It is a very dangerous drug," said Dr. Brian Olshansky, a cardiologist at the University of Iowa who said he often uses the drug to place patients in deep sedation for certain heart procedures. "It is not for sleep. I cannot imagine anyone would use this outside a very regulated environment such as the availability of emergency respiratory equipment."
Propofol Poses Dangers to Abusers
One main reason for this, he said, is the speed with which the drug has its effect.
"It rapidly induces unconsciousness and apnea," Olshansky said. "People stop breathing within seconds of being given the drug."
These characteristics of the drug make it an exceedingly unusual choice for abuse, said Dr. Jeff Guy of Vanderbilt University, who said such a situation would represent "a quantum leap in the issue of substance abuse."
But despite the effects and risk profile of the drug, Nearman said that patients who've had the drug describe it as inducing "a very pleasant sleep" that "has the potential to be habit-forming."
And Dr. Bruce Goldberger, chief of forensic pathology at the University of Florida, noted that the drug "also acts as an aphrodisiac in men -- it has been reported that men have very vivid sexual dreams while under Propofol anesthesia."
Federal, Local Officials Continue Investigation
The discovery of the drugs in Jackson's home marks a point at which federal agents had begun to define their role in the Michael Jackson death probe and shape their team which would work to assist the Los Angeles Police Department.
The LAPD robbery and homicide division is the lead agency on the case, and the Drug Enforcement Administration's Diversion Division is assisting.
Meanwhile, a lawyer for Dr. Conrad Murray, Jackson's personal physician, said the doctor had prescribed neither OxyContin nor Demerol to the pop icon. He has not commented on Diprivan.
ABC News' Roger Sergel contributed to this report.