Police want to question Dr. Conrad Murray, a Las Vegas physician who with Michael Jackson when the 50-year-old King of Pop went into cardiac arrest Thursday.

According to the frantic 911 call (listen to it here) made from inside Jackson's rented L.A. home, Murray, 51, had administered CPR on the singer before paramedics arrived. Murray also later accompanied the ambulance to the UCLA Medical Center, where Jackson was pronounced dead at 2:26 p.m. PST.

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Investigative reporter Diane Dimond -- who has covered Michael Jackson for years -- said on CBS' The Early Show Saturday Edition: "If he was the only doctor on the scene and, as we heard in the 911 call, worked on Michael Jackson for quite awhile before they called 911, he may be culpable of something. I hope he's got a good lawyer."

Although toxicology test results won't be available for up to six weeks (a preliminary autopsy showed no foul play), Jackson family attorney Brian Oxman told Usmagazine.com he fears prescription drugs played a role. "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," he told Us.

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A spokesman for the Los Angeles County Coroner's Office has said they know that Jackson had been taking prescription drugs but needed to find out the specific medications.

Murray -- who reportedly is licensed in California, Nevada and Texas and has an office in Houston -- had treated Jackson for three years. Two weeks ago -- around the time Murray reportedly announced he was shutting down his private practice -- Jackson requested that Murray be with him, according to reports. He was then hired by AEG Live, which was producing Jackson's upcoming London shows.

Dimond, the reporter who covered Jackson, she was "stunned to learn this doctor [Murray] was hired by the concert promoter (AEG Live), I guess at Michael's request. He wanted to have a doctor with him. I worked in Hollywood for many years, (for) most of the '90s, and when the celebrities have a personal doctor, it's really a prescription writer; it's really a personal drug supplier."

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But she said she's "covered Michael Jackson since 1993. He has always had an entourage of people around him of people who do exactly what he says, or they're not there anymore. As to who is responsible, I believe in personal responsibility: You put a pill in your mouth, you did that, you put a needle in your arm, you did that. But ... there were enablers around him."

She believes drugs led to his death.

"I'm not the only one who says he's a drug addict. ... But I think so," she said. "The coroner said (they saw) no visible signs of trauma, so that tells me his anorexia (Jackson reportedly weighed 125 lbs. at the time of his death) did not cause a diseased heart. They didn't say they saw a diseased heart or a bad ventricle or artery. So, it's something else that killed him."

Even Jackson pal Liza Minnelli has her suspicions: "When the toxicology test comes out," she said on The Early Show earlier this week, "you-know-what's gonna break loose."