Michael Jackson’s corpse had the hallmarks of longtime intravenous drug use, including arms riddled with needle marks and collapsed veins, say sources familiar with the medical examiner’s preliminary findings. Buttressing this autopsy result, an employee in Jackson’s entourage during the mid to late 1980s claims she saw Debbie Rowe, a nurse for one of the superstar’s doctors and later his wife and the surrogate for his two oldest children, visiting Jackson at his home and injecting him with an unknown substance.

Given the circumstances surrounding Jackson’s death, any Rowe involvement in administering drugs could become an issue if she seeks custody of the two oldest children.

These reports of longstanding IV-drug use raise new questions about whether the pop star, who traveled with an anesthesiologist during his HIStory tour in the mid-'90s, died from the improper administration of some of the anesthesia drugs seized by investigators in his home after his death last week.

While the Los Angeles Police Department and the federal Drug Enforcement Administration are narrowing their list of enabling doctors, The Daily Beast discussed Jackson’s medical history with several people familiar with it and has uncovered new details, including a role played by Rowe’s ex-boss, Dr. Arnold Klein. On Tuesday, I reported that Elizabeth Taylor had sought help for her own prescription-drug and alcohol problems in the mid to late 1980s and that she and Jackson both patronized Klein, the Beverly Hills dermatologist who was one of her main prescription sources, based on an account she gave another physician treating her at the time. That second doctor knew Jackson as a friend, not a patient, and thought the Taylor-Klein combination could be “toxic” for Jackson, and twice warned the pop star. But Jackson, who idolized Taylor and praised Klein, would hear none of it, according to a source familiar with the conversations between Jackson and his doctor friend.

The details about Rowe solidify that account of a strong Jackson-Klein link. As a nurse working for Jackson’s treating physician, it is possible that Rowe was doing nothing more than injecting medications properly prescribed by Dr. Klein, and Rowe was merely making a house call. It is also possible that Rowe, as a personal friend and medical professional, was administering another doctor’s prescription at Jackson’s request. A source close to the police investigation told The Daily Beast that Debbie Rowe is definitely not the subject of any probe into Jackson’s demise. But given the circumstances surrounding Jackson’s death, any Rowe involvement in administering drugs could become an issue if she seeks custody of the two oldest children, as she suggested last week that she might, despite a reported $8 million payout to relinquish her parental rights. In response to calls seeking clarification on the circumstances of these injections, Rowe’s attorneys had no comment.

A Los Angeles Police spokesman refused to confirm or deny whether Dr. Klein was one of five physicians reportedly the subject of their Jackson investigation. Neither Dr. Klein nor his attorney would comment for this article. But Dr. Klein told Diane Sawyer on Good Morning America this morning that he has not been questioned by any investigators and said he was not one of the final five physicians being probed. Moreover, while not addressing any issue of early drug prescriptions to Jackson he contended, "I didn't give him the crap they are talking about....I was not one of the doctors who participated in giving him an overdose of drugs or too much of anything."

This probe into Jackson’s physicians has already degraded into finger-pointing within the LAPD, The Daily Beast has learned. Specifically, officials are upset that there was a multi-day delay between the time Jackson’s body was removed from the house and the execution of a search warrant, which resulted in the removal of several bags of prescriptions and medical equipment from the house. That timeline has raised questions about whether it gave a chance for anyone in the Jackson entourage to destroy possibly incriminating evidence.

An employee at the house, rented by Jackson’s concert promoter AEG, told The Daily Beast that he had once seen—several weeks before Jackson’s death—Dr. Conrad Murray administering an intravenous solution to the pop star in his bedroom. Murray was the physician in Jackson’s house when he died. When the employee asked a more-seasoned member of Jackson’s entourage what was happening, he was told that Jackson needed to be rehydrated with vitamins and fluids after his grueling rehearsals for his upcoming concert series in London and that it “was no big deal.”

Murray’s lawyers, when asked about this new revelation, told me, “Per our agreement with the Los Angeles investigators, we cannot confirm or deny the existence of any IV drugs or medical equipment in Mr. Jackson’s bedroom or whether Dr. Murray administered any such drugs to Mr. Jackson.”

The Daily Beast has learned that investigators will likely serve search warrants this week, possibly as early as today, on several doctors who might have enabled Jackson’s addiction. One investigator bristled when I asked if the swirl of public accusations, coupled with the delay of executing the warrants, meant the medical offices in question may have had the opportunity to destroy incriminating evidence and records. “We are doing it correctly and methodically,” he told me. “We will have a case when we are finished.”

Gerald Posner is the award-winning author of 10 investigative nonfiction bestsellers, ranging from political assassinations, to Nazi war criminals, to 9/11, to terrorism ( www.posner.com). Posner lives in Miami Beach with his wife, the author Trisha Posner.