Celebrity Web site TMZ is reporting there were "large amounts of prescription medications" on the nightstand when paramedics arrived at her Hollywood home, and that Murphy was "complaining of shortness of breath and severe abdominal pain" in the week before she died.
"She always denied any relationship to drugs," US Weekly Entertainment Director Dena Sansing told CBS News. "She said she had never tried it. She said the strongest thing was Sudafed -- it wasn't her thing."
But at least one leading pathologist tells "The Early Show" he'd bet a lethal combination of prescription drugs was involved.
"It's possible, certainly" (that Murphy died of natural causes), Dr. Cyril Wecht told "Early Show" co-anchor Maggie Rodriguez Tuesday, "and usually, it will be some kind of a congenital heart condition. But in most of those cases, the patient will be aware that there is some heart problem.
"When you have a 32-year-old person dying suddenly, and especially a celebrity in Los Angeles, you can place your bet down that it's going prove to be a case of acute combined drug toxicity. And I bet you that this young lady tragically died in the same way that Michael Jackson did, and Anna Nicole Smith, and her son, Daniel Smith, and Heath Ledger -- a combination of drugs that had been prescribed for her, prescribed for her husband, for her mother, in some fictitious names, probably by doctors who are very, very quick to make available anything that celebrities want, sometimes using knowingly fictitious names.
"So, even though these drugs are, quote, legal, unquote, they are, many times, illegally obtained. And it's a tragedy. And it's being played out everywhere in America every day, and we only come to know about it when it involves celebrities."
What leads Wecht to conclude drugs were involved here?
"I am aware of some of the drugs that were found. One of them was a drug that was involved with Michael Jackson, Adivan. One of them was a drug that was involved with Anna Nicole Smith, Klonopin. Two of the drugs are pain relievers, Hydrocodone, which we frequently see in these cases, and Vicoprofen, a form of Vicodin. So, I guarantee you that, if the pathologists at the Los Angeles coroner's office had found something dramatic, like a heart attack, like a stroke, or like something of a definitive nature, would you have heard about it. The fact that they say that they're going wait for toxicology tests and it will take a couple of months, you can be sure that this is going to prove to be a case of acute combined drug toxicity. A tragedy."
Officially, Assistant Chief Los Angles County Coroner Ed Winter said to reporters that an autopsy had been conducted and officials were awaiting the results of toxicology and tissue testing before determining an official cause of death. It could take up to six weeks before a determination is made public.
Officials also interviewed Murphy's personal physician and examined prescription drugs taken from her home. None of the medications was illegal, reports said.
Additional Coverage of Brittany Murphy's Death
Paramedics tried to revive Murphy early Sunday, but she was pronounced dead at Cedars-Sinai Medical Center. The hospital said she died of cardiac arrest.
The autopsy found no signs of trauma to the body of the 32-year-old star of "Clueless" and "8 Mile." Police say they don't suspect foul play.
Winter said Murphy's family reported she had been ill and that could have contributed to her death. He said he had no further details about the medication taken from the home Murphy shared with her screenwriter husband Simon Monjack.