The agency's involvement is a sign that the use or abuse of prescription drugs may be suspected, a law enforcement official says. The state attorney general's office is also joining the probe.

Reporting from Los Angeles and Washington - The Los Angeles Police Department's request for federal drug agents to join the investigation of Michael Jackson's death indicates that illegal activity may be suspected in the dispensing of painkillers, sedatives, antidepressants or other medications to the 50-year-old entertainer, according to a law enforcement official.

Some of Jackson's friends, family and confidants have come forward to say that he was abusing painkillers and other prescription drugs over a long period of time, and that perhaps others in his ever-changing entourage kept him supplied, which could be illegal. The DEA is investigating various possibly related activities, said the official, who spoke on condition of anonymity because the investigation is ongoing.

The LAPD's request for the federal Drug Enforcement Administration to get involved in the case is typical because of the agency's experience and jurisdiction in investigating suspected drug overdoses and other deaths in which the use or abuse of drugs and prescription medication is suspected to have played a role, the official said.

In another sign of a widening probe, California Atty. Gen. Jerry Brown said Thursday that his office is helping the LAPD. Brown said state law enforcement officials are using a computer database to mine for information on prescription drugs that will be passed on to investigators with the LAPD's Robbery-Homicide Division.

The database contains the name of every doctor that prescribes controlled medicine, the person for whom the drug is prescribed, the quantity and the date. "We are using it to probe for relevant information in the Jackson case," Brown said. "If it's about doctors, drugs and patients or anything that touches that, it's in our database. We've been in touch with the LAPD, and I've talked to" Police Chief William J. Bratton.

In March, prosecutors charged Anna Nicole Smith's boyfriend and two of her doctors with repeatedly supplying the former Playboy centerfold with addictive prescription drugs since 2004, nearly three years before she died of an overdose.

The DEA has the resources and expertise to investigate such cases, including federal drug agents and specially trained "diversion investigators." These investigators don't carry badges or guns, but they investigate pharmacies, doctors and so-called pill mills - black market storefronts and Internet sites that provide drugs and medication, often bootleg varieties, without regard to obtaining the proper prescription or quality control, the official said.

Often, the crimes involve the diversion of legitimate drugs for illegitimate medical purposes, such as supplying addicts with high-strength painkillers like Oxycodone.

Dr. Conrad Murray, a cardiologist with offices in Las Vegas and Houston, was identified by a Jackson advisor as the singer's personal doctor of three years and the man tapped to safeguard his health during the grueling comeback concert series that was supposed to start this month in London.

The law enforcement official said there was no immediate indication that Murray had done anything wrong or that Jackson was getting prescription drugs illegally or inappropriately, including medication he did not need or doses that were too large or administered over too long a period of time.

But, he said that in "investigations such as this, that's what they're looking for." The Los Angeles County coroner's office has said that it was conducting tests to determine whether Jackson overdosed on prescription medications that he was taking.

The DEA's role in the investigation was still being worked out. "A lot of drugs, you need a prescription each time you get a refill. They will be looking at sources of [the drug] supply, where are the drugs coming from, are they doing criminal stuff, such as writing many, many prescriptions and having people fill them around town?" the official said.

The DEA will also look into how Jackson's doctors stand with the agency, which requires them to register for the authority to prescribe certain medications, the official said. Also, the DEA will investigate whether those doctors had a "face-to-face relationship" with Jackson, which is required.

In a number of cases, the official said, the DEA has found doctors dispensing medications without having diagnosed or even seen the patient, which can be illegal.

A doctor can lose his or her license if found to be improperly or illegally administering medications, especially in cases in which a patient dies or is gravely injured.

In extreme cases where death occurs, law enforcement officials said, doctors or other "enablers" can be charged with criminal manslaughter if they obtain or administer medication in a manner that displays a reckless disregard for human life.

Authorities removed prescription drugs and other medical evidence from the Holmby Hills home where Jackson died.

A law enforcement source told The Times that Propofol, a powerful anesthetic, was among the drugs recovered.