Michael Jackson's doctor administered the powerful drug police believed killed the music superstar, CNN quoting a source with knowledge of the investigation reported.
Doctor Conrad Murray has become the focus of the probe into Jackson's death amid reports that bottles of the potent anesthetic propofol were found at the star's mansion after his tragic June 25 demise.
A report on CNN's website did not give further information and a spokeswoman for Murray's legal team refused to comment. A spokesman for the Los Angeles Police Department also declined to comment.
Jackson's cause of death has been deferred pending the outcome of toxicology tests following a June 25 post mortem. Those test results could be released later this week.
The report comes just days after federal agents and detectives swooped without warning on Murray's Houston office, revealing for the first time in a search warrant that Jackson's death was being treated as possible manslaughter.
Propofol is used in hospitals to induce unconsciousness in patients ahead of major surgery. Experts say it should only be administered by a trained anesthesiologist and there could be no reason for it to be in Jackson's home.
Lawyers for Murray said in a statement last week the doctor was keen to assist authorities in their investigation and was preparing for a third meeting with police after two earlier interviews.
"The coroner wants to clear up the cause of death, we share that goal," attorney Ed Chernoff said in a statement.
Murray is currently in Las Vegas, his legal team said, and Chernoff insisted that "based on Dr Murray's minute-by-minute and item-by-item description of Michael Jackson's last days, he should not be a target of criminal charges.
"Dr Murray was the last doctor standing when Michael Jackson died and it seems all the fury is directed toward him," Chernoff said.
"Dr Murray is frustrated by negative and often erroneous media reports, he has to walk around 24-7 with a bodyguard. He can't operate his practice."
In the immediate aftermath of Jackson's death, friends of the singer's family said the clan had "unanswered questions" regarding Murray.
"They (the family) are suspicious of this doctor and they have real reason to be because any other doctor would say 'Here's what happened in the last hour of his life and I was there. I gave him some medicine,'" family friend and civil rights activist Jesse Jackson said.
"(Murray) owes it to the family and to the public to say, 'These were the last hours of Michael's life and here's what happened.' That's a reasonable expectation."