A police spokesman confirmed they want to interview the singer’s personal doctor who was present when the singer stopped breathing at his home in the exclusive Holmby Hills area of the city.
Police towed away the doctor's BMW for forensic examination.
A LAPD spokesman said:” The car belonged to Mr Jackson’s personal physician.
"It was impounded as police have been unable to interview him and the car could contain medication or other evidence for the coroner.”
The house Jackson rented, once home to Sir Sean Connery, is being treated as a possible crime scene.
The police spokesman would not confirm the name of the doctor being sought for questioning.
Speculation is mounting in the US that Jackson stopped breathing and suffered a heart attack after taking an injection of a morphine-based painkilling drug.
Unconfirmed reports suggested Jackson had been taking daily injections of Demerol, the commercial name for pethidine.
Pethidine is known to have dangerous side effects including cardiac arrest if used wrongly. Police claimed they found a supply of the drug and syringes at Jackson's previous home, the Neverland Ranch near Santa Barbara, California, five years ago as part of their investigation into child abuse.
A post mortem examination is under way to determine the cause of Jackson's death, though it could be weeks before toxicology reports reveal whether he had any drugs in his body.
The night before he died, he had been rehearsing for his sellout series of concerts in London, which were due to start in two weeks.
His recent bid to prepare for his comeback, including rehearsals lasting up to 10 hours, had left him weak and gaunt, according to members of his crew.
"He was frail, you might say," said Patrick Woodroffe, a lighting director. However he added that the singer seemed to have enjoyed a burst of energy in what would prove to be his final performance ever. "He came on stage and he was electric. It was like he had been holding back and suddenly he was performing as one had remembered him in the past."
The Jackson family lawyer, Brian Oxman, blamed members of Jackson's entourage for "enabling" him to take drugs, but did not name names.
Mr Oxman compared Jackson's death to that of Anna Nicole Smith, the former Playboy model who was found dead two years ago at a hotel in Florida, with an overdose of prescription drugs blamed for her death.
Mr Oxman said: "I warned against this situation. I thought his problem was severe. I made reference to what happened to Anna Nichol Smith, but this exceeded it in severity."
Mr Oxman, who was at the UCLA hospital with the Jackson family when he died, said Jackson first started taking pain medication after his hair caught fire during the filming of a Pepsi commercial in the early 1980s.
The drugs became a regular part of his life, Mr Oxman said, when Jackson later fell off a stage and suffered a broken leg and a cracked vertebra.
"I will not hold my tongue," he said. "I will speak out and I will speak out loud."
Mr Oxman said Jackson had also been under intense pressure because of the forthcoming tour, which he had hoped would clear his debts of more than £200 million.