Michael Jackson's doctor administered the drug which killed the singer at his Los Angeles home last month, a law enforcement official has said.
The official, speaking on the condition of anonymity because of the ongoing investigation, told the Associated Press Dr Conrad Murray regularly gave Jackson Propofol to help him sleep.
Police believe Dr Murray last administered the drug to Jackson through an IV shortly after midnight on June 25, the official said.
The 50-year-old singer died just over 12 hours later at a Los Angeles medical hospital.
Propofol, which is commonly used to help induce a patient into unconsciousness before surgery, has become the focus of the police's investigation into Jackson's death.
Previous reports have claimed the powerful sedative, also known as Diprivan, was found at the singer's rented home in Holmby Hills.
According to the official, police are investigating the possibility that different doctors had administered Jackson with the drug since he began using it two years ago.
Dr Murray's lawyer Edward Chernoff told the Associated Press: "We will not be commenting on rumors, innuendo or unnamed sources."
The Los Angeles Coroner's office has deferred Jackson's cause of death pending the results of toxicology tests, which are expected shortly.
Court papers last week showed Dr Murray had been identified as the target of a manslaughter investigation into Jackson's death.
Micahel Jackson
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