Although the exact cause of Michael Jackson's death remains a mystery, many have suspected a possible drug overdose to be the culprit as fans and family await the result of Jackson's autopsy, due in weeks.

The star has been reportedly taking a painkiller Demerol, a drug similar to morphine, but has since become addicted to the prescription drug, according to the Sun.

A good friend of Jackson, Liza Minnelli, told CBS's The Early Show that the singer's autopsy results will create a stir when they come out.

All of us who knew him well really know what he was like,” Minnelli said. “ I'm sure when the autopsy comes all hell's going to break loose. So, thank God we're celebrating him now.

Brian Oxman, who served as the Jackson family attorney for more than 20 years, told US Magazine that the star had been taking medication, but did not want to speculate on the cause of death.

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,” Oxman said.

Jackson was under enormous stress to perform in the 50 concerts at London O2 centre, which was to begin in July. He is reported to have told his fans earlier outside his LA studio he was not sure how he will cope with the 50 shows as he originally wanted to do only 10 shows touring around the world.

The 50-year-old Jackson -- who suffered cardiac arrest and was pronounced dead at 2:26 p.m. PST -- was said to have no particular health concerns except.

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.