Michael Jackson rehearses for the London concerts at the Staples Center in Los Angeles on June 23. His former nurse alleged he asked for prescription sedatives before he died. (Kevin Mazur/AEG/Getty Images/Associated Press)

A law enforcement official speaking on condition of anonymity revealed Friday that the sedative Diprivan was found in the home the late pop star Michael Jackson was renting in Los Angeles.

Diprivan, also called Propofol, is a powerful anesthetic administered intravenously in operating rooms to induce unconsciousness, and it would be unusual to see it in a private home.

The cause of Jackson's death on June 25 is unknown, but federal drug enforcement officials have been called in to investigate.

Among the allegations they are investigating are reports that Jackson used pseudonyms to acquire prescription painkillers, sedatives and antidepressants.

A nurse who once served as Jackson's nutritionist alleged publicly that the pop star was under stress and had asked for Diprivan as he prepared for the London, England, concerts he was scheduled to give this month.

Cherilyn Lee said the singer had been having trouble sleeping. She said she refused to give him the drug he wanted, but wondered if someone else might have.

"I told him, 'You might not wake up the next morning. You don't want to do that,'" Lee said on Tuesday.

There is potential for criminal charges against doctors who might have knowingly over-prescribed, the U.S. Drug Enforcement Administration said.

According to friends, Jackson, 50, had suffered chronic pain dating back to an accident filming a Pepsi advertisement in 1984 when his hair caught fire and his scalp was burned.

His use of painkillers is said to have increased during his 2005 trial on child abuse allegations. He was acquitted on those charges.