Reports: Jackson had shot of Demerol before death

Los Angeles police spokeswoman Karen Rayner said coroner's investigators were seeking to interview the doctor but said she did not know the doctor's identity. She stressed the doctor was not under criminal investigation.

"His car was impounded because it may contain medications or other evidence that may assist the coroner in determining the cause of death," Rayner said.

Web sites and news services painted a picture of family that had become increasingly worried about the singer's use of prescription drugs.

An autopsy of the pop star is reportedly under way. He died after being found in cardiac arrest at his home. Full toxicology results may not be known for weeks.

Jackson collapsed and stopped breathing after the injection at his rented home in Los Angeles, sites reported.

The Sun reported that Jackson aides told emergency room doctors at UCLA Medical Center, where he died, that the star had collapsed after an injection of Demerol -- a powerful pain-killing drug similar to morphine and known to carry a risk of cardiac arrest.

"Shortly after taking the Demerol he started to experience slow, shallow breathing," the newspaper quoted one source as saying. "His breathing gradually got slower and slower until it stopped." The hospital has not confirmed that account.

As far back as 2006, members of Jackson's family were terrified that his escalating dependence on prescription drugs had become a danger to his life -- and attempted an intervention in Las Vegas, People.com reported. But Jackson said he wasn't on drugs.

Brian Oxman, a former attorney of Jackson's and a family friend, said he was concerned about Jackson's use of painkillers and he warned the singer's family about possible abuse.

"I said one day, 'we're going to have this experience.' And when Anna Nicole Smith passed away, I said 'we cannot have this kind of thing with Michael Jackson,'" Oxman said Friday on NBC's "Today" show. "The result was, I warned everyone, and lo and behold, here we are. I don't know what caused his death. But I feared this day, and here we are."

Oxman said Jackson had been struggling to cope with pain from several performance injuries, including a damaged vertebra and a broken leg, which had been interrupting scheduled rehearsal for his upcoming London tour dates.

The circumstances of Jackson's death remain unclear. LAPD robbery-homicide detectives have opened an investigation, though they emphasized that there was no evidence of criminal wrongdoing.