LOS ANGELES — The powerful sedative Diprivan was found in Michael Jackson's home, a law enforcement official said Friday as the city planned for a massive crowd at the singer's memorial service.

Diprivan is an anesthetic widely used in operating rooms to induce unconsciousness. Also known as Propofol, it's given intravenously and is very unusual to have in a private home.

The law enforcement official spoke on condition of anonymity because the person was not authorized to speak about the matter.

A Los Angeles Police spokesman, Lt. John Romero, declined to discuss the case. "It's an ongoing investigation," he said.

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

At the downtown Staples Center, where Jackson's memorial will be held Tuesday morning, Assistant Police Chief Earl Paysinger said anywhere from 250,000 to 700,000 people could try to reach the arena, even though only 17,500 tickets will be available.

City Councilwoman Jan Perry urged people to stay home and watch the memorial on TV. There will not be a funeral procession through the city.

Tickets to Jackson's memorial service will be free. They can be obtained by registering at Staplescenter.com. There will be 11,000 tickets for seats inside Staples Center and 6,500 for seats in the adjacent Nokia Theatre, where fans can watch a simulcast. On Saturday night, 8,750 names will be randomly selected to receive two tickets each.

No details about the memorial service itself were released.

Jackson was known to have suffered from severe insomnia. In the weeks before his death, Cherilyn Lee, a registered nurse who was working with the singer, said Jackson pleaded for Diprivan amid the stress of preparing for a massive series of comeback concerts.

Lee said she repeatedly rejected his demands because the drug was unsafe.

Told Friday that Diprivan had been found at Jackson's house, she said, "I did everything I could to warn him against it."

Jackson had trouble sleeping as far back as 1989, said one of his former publicists, Rob Goldstone, who spent a month on the road with Jackson during the "Bad" tour.

"He had very bad nightmares, he found it very difficult to sleep," Goldstone said.

Diprivan, which has a milky appearance, is sometimes nicknamed "milk of amnesia." Last fall, doctors from the Mayo Clinic warned at a conference that in rare cases, Diprivan can trigger an irreversible chain of events leading to heart dysfunction and death.