Although the exact cause of Michael Jackson's death remains unknown, Brian Oxman - who has served as the family's attorney for more than 20 years - suspects prescription drug abuse may have played a role.

"I don't know what caused Michael's death, and I don't want to speculate as to what the causes are," Oxmon tells Usmagazine.com. "I only know that I warned them there was the misuse of prescription medications by people who were enabling him; his handlers, folks who should never have been permitted to allow him to use those medications in the manner I observed."

"So is that the cause of it? I don't know," he continues. "People die from various and sundry causes - they have congenital malformations of the heart, they have difficulty with various infections. I don't know what Michael Jackson's death is a result of."

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Oxmon says the 50-year-old Jackson -- who suffered cardiac arrest and was pronounced dead at 2:26 p.m. PST Thursday -- "had no particular health concerns except that he had broken his leg many years ago, and it hurt him."

"He had cracked a vertebrae in his back and he took painkillers to try to ease the pain," he says. "And now we find ourselves here. I don't know if the two are connected. I had warned that the misuse of medications would result in this, and I am heartbroken that we are here."

Though some reports claim Jackson may have overdosed on Demerol, Oxmon declined to elaborate on the types of medications Jackson was taking "because it is something which is private to Michael, and we'll have to wait for the toxicology reports before we jump to any kind of conclusions. I only know that I warned that his day may come. And lo and behold, here we are."

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An autopsy is planned for Friday, but results may not be final until toxicology tests can be completed, which could take several days and sometimes weeks. Los Angeles County Coroner Investigator Jerry McKibben said if a cause can be determined by the autopsy, they will announce the results.

"We will have to wait to see what the toxicology reports have to say, what the coroners report has to say," Oxmon says. "When that happens, I will be very vocal. It could very well be he died from natural causes, in which case, my gosh, the tragedy becomes even greater."

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Jackson was set to headline 50 sold-out shows, billed "This Is It," at London's O2 Arena beginning in July -- his final London performances. Oxman did not know if Jackson had been examined before the tour, but "he has been in good health," he says.

As he rehearsed for the concerts, "He had been making his very best efforts to be pain-free, but it's been very difficult to him," Oxmon says.

"But I was not aware, and I don't think any of the family members were aware, of any kind of specific condition which was causing him any kind of medical or physical difficulty," he continues. "I don't know what the extent of his exercise routine was. But I do know that he was making good progress toward getting ready to perform at the show."

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