ABC News has learned that the autopsy of Michael Jackson found the powerful anesthetic propofol, as well as several prescription drugs, in his system, and law enforcement sources say that investigators believe their final report will list the propofol as a "contributing factor" in his death.
Jackson's personal doctor, Conrad Murray, who was with him when he died June 25 at his rented California home, has been identified in court papers as the subject of a manslaughter investigation.
Murray's lawyers have maintained for weeks that the doctor was simply a witness in Jackson's death and had nothing to do with it.
"Dr. Murray didn't prescribe or administer anything that should have killed Michael Jackson," Murray's lawyer Ed Chernoff said July 6.
Murray's lawyer has specifically said his client never gave Jackson Oxycontin or Demerol, but he hasn't made the same claim about propofol, an anesthetic used to knock patients out for diagnostic tests or surgery that is recommended for use only under strictly controlled conditions.
Murray, who was hired to monitor the entertainer for his planned "This Is It" tour, was called to Jackson's house June 24 and was the person who found him unconscious, not breathing in bed the next day.
Murray has been widely criticized by medical professionals for waiting more than 30 minutes to call 911 and for performing CPR on a bed instead of a hard surface, but he has continually denied giving Jackson any drug that could have killed him.
He has been secluded at his Las Vegas home and reportedly goes out with a security detail due to death threats.
Late today, The Associated Press reported that a law enforcement official said investigators believed Murray administered the shot of propofol that would end Jackson's life.
Chernoff declined to comment on the report, saying only, "We will not be commenting on rumors, innuendo or unnamed sources."
Michael Jackson's Nurse Refused Him Propofol
Cherilyn Lee, a registered nurse and nutritionist who worked for Jackson, said the singer begged her to give him propofol in the days before his death. She refused to help him obtain it.
Lee told ABC News the pop star had often complained of not being able to sleep more than a few hours at a time and wanted propofol to ease his insomnia.
"The problem with you telling me you want to be knocked out," Lee said she told him, is "you might not wake up the next morning. You don't want that."
Weight Loss Drugs, Muscle Relaxants Found in Jackson Doctor's Office
When investigators searched Murray's Texas office earlier this month, among the items seized were a vial containing 27 tablets of the weight loss drug phentermine, a vial containing a tablet of the muscle relaxant clonazepam, a photocopy picture of Murray, Rolodex cards, public storage receipts, and a receipt for a "Cricket" phone, according to the search warrant.
Other items seized from his storage unit, according to the court records, included two computer hard drives and a "Texas Department of Public Safety controlled substance registration." Authorities also obtained a suspension notice from a Houston hospital.
The search warrants specifically directed officers to "seize and examine all items, including but not limited to, billing records, medication orders, transport receipts, billing receipts, medical records and computerized medical records, for implements and instruments used in the commission of a crime."
The warrants told police they were "commanded to search ... for property or items constituting evidence of the offense of manslaughter that tend to show that Dr. Conrad Murray committed the said criminal offense" and ship any evidence found to officials in California.
Jackson Had Addictions to Propofol, Oxycontin, Demerol
In the aftermath of his death, Jackson's addiction to a variety of drugs was revealed, including propofol (trade name Diprivan), the analgesic Demerol and the painkiller Oxycontin. Track marks found on his arms support the theory that he was addicted to propofol.
Prescription medications found inside Jackson 's $100,000 per month rental home included ones in his name and ones in other names, including ones that appeared to investigators to be aliases. The medications had been prescribed by multiple doctors.
Jackson Drug Stockpile 'Typical for an Anesthesia Cart'
Methadone, Fentanyl, Percocet, Dilaudid and Vicodin were among the 20 drugs also found in Jackson's rental home.
Medical experts contacted by the ABC News medical unit said that the amount of medications reportedly found in Jackson's rented home was "jaw-dropping" and "amazing."
"That list is enough to put down a swarm of zombies," said Richard Bradley, chief of the Division of EMS and Disaster Medicine at the University of Texas Health Science Center at Houston.
"The list ... would be typical for an anesthesia cart in an operating room or what you might find in a recovery room, ICU, ED, etc. Definitely not what you'd expect to find in a home," said Joseph Ornato, chair of the department of medicine at Virginia Commonwealth University.
Murray is not the only doctor who has been eyed by law enforcement in the wake of the pop star's death. Law enforcement sources confirmed to ABC News earlier this month that a small group of doctors who treated Jackson before his death are being questioned as to their involvement with Jackson's alleged drug use.
On July 15, California Attorney General Jerry Brown said his office was running several doctors' names and several potential aliases through its prescription drug database to aid police investigating Jackson's death.