Los Angeles police are calling it "an ongoing investigation."

That comes after a law enforcement official, speaking on condition of anonymity, revealed that the drug Diprivan was found in Michael Jackson's home following his death. Diprivan is an anesthetic given intravenously and widely used in operating rooms to induce unconsciousness.

The cause of Jackson's death has not been determined, and autopsy results are not expected for several weeks.

Authorities are investigating allegations that the 50-year-old Jackson had been consuming painkillers, sedatives and antidepressants. Any criminal charges would depend on whether Jackson had been overly prescribed medications, given drugs inappropriate for his needs, or if doctors knowingly prescribed Jackson medications under an assumed name.

Jackson was known to have suffered from severe insomnia. One of his former publicists says Jackson's sleeping problems date back as far as 1989 and include "very bad nightmares."