Michael Jackson's personal doctor gave him a powerful anesthetic through an intravenous drip to help him sleep, and authorities believe the drug caused the pop singer's death, a law enforcement official told the Associated Press.

The official, who spoke on condition of anonymity, said Jackson regularly received the anesthetic propofol and relied on it like an alarm clock.

A doctor would administer the drug when Jackson went to sleep, then would stop the IV drip when the singer needed to wake up.

On June 25, the day Jackson died, Dr Conrad Murray gave Jackson the drug through an IV after midnight, the official said.

Murray's lawyer, Edward Chernoff, has said the doctor "didn't prescribe or administer anything that should have killed Michael Jackson".

When asked Monday about the law enforcement official's statement, Chernoff said: "We will not comment on rumors, innuendo or unnamed sources."

In a statement posted online Monday, Chernoff said: "Things tend to shake out when all the facts are made known, and I'm sure that will happen here as well."

Toxicology reports are pending, but investigators are working under the theory that propofol caused Jackson's heart to stop, the official said.

Jackson is believed to have been using the drug for about two years, and investigators are trying to determine how many other doctors administered it, the official said.

Using propofol to sleep exceeds the drug's intended purpose.

The drug can depress breathing and lower heart rate and blood pressure.

Because of the risks, propofol is supposed to be administered only in medical settings.

The official also provided a glimpse into how the pop star was living in the weeks before he died, describing the room in which Jackson slept in his rented Beverly Hills mansion as outfitted with oxygen tanks and an IV drip.

Another of Jackson's bedrooms was in shambles, with clothes and other items strewn about and handwritten notes on the walls.

The temperature was stiflingly hot when authorities arrived at the house.

Gas fireplaces and the heating system were on high because Jackson complained of feeling cold, the official said.

(China Daily/AP July 29, 2009)