LOS ANGELES (AP) — Police and federal drug agents investigating the death of pop star Michael Jackson have seized documents and computer records from his doctor's clinic as they narrow their focus in what could become a criminal probe.

Almost one month after the King of Pop died, investigators from the Drug Enforcement Administration and Los Angeles police on Wednesday raided the Houston clinic of Conrad Murray, the personal physician Jackson hired in May to look after him as he prepared for a series of comeback concerts in London.

Among the items seized were files copied from an office hard drive and 21 documents. Murray's lawyer, Edward Chernoff, said authorities believed the evidence "constituted evidence of the offense of manslaughter." He did not provide further details, and police said they do not consider Murray to be a suspect.

Authorities are investigating several doctors who associated with Jackson to see if they inappropriately provided him with prescription drugs.

A manslaughter charge would require proof there was a reckless action that created a risk of death or great bodily injury. If a doctor is aware of the risk, there might also be an issue of whether the patient was made aware of that risk and decided to take it.

In the weeks since he died, rumours about what killed him have been rife. Several members of Jackson's family have said they suspect foul play. Investigators appear to be focusing on a powerful anesthetic, propofol. The drug was found in the Beverly Hills mansion Jackson was renting, according to a person with knowledge of the investigation who is not authorised to speak publicly.

Wednesday's raid of Murray's clinic in a lower-income area of north Houston was the most visible sign yet that Murray remains a central figure in the investigation.

On June 25, Murray found Jackson unconscious in a bedroom of Jackson's rented mansion, his lawyer has said, and tried to revive him and ultimately helped summon paramedics.

Police have twice interviewed Murray, including at the Los Angeles hospital where Jackson was taken and pronounced dead. The coroner's office wanted its own interview, which the lawyer agreed to; it may happen today without Murray present, according to Miranda Sevcik, Chernoff's spokeswoman. Chernoff would answer questions on the doctor's behalf.

"Based on Dr. Murray's minute-by-minute and item-by-item description of Michael Jackson's last days, he should not be a target of criminal charges," Chernoff had said in a statement a day before the raid. "Dr. Murray was the last doctor standing when Michael Jackson died, and it seems all the fury is directed toward him."

Murray also has a clinic in Las Vegas but there was no sign of activity there. Doors were locked and curtains drawn at his practice, Global Cardiovascular Associates.

Also on Wednesday, Los Angeles County coroner's officials were piecing together Jackson's medical history from subpoenaed records related to nutritionist Cherilyn Lee's treatment of Jackson, according to Lee's spokeswoman, Belinda Foster.

The registered nurse is co-operating with investigators but required a subpoena because the records were protected by law, Foster said.

The coroner's office did not return calls on Wednesday seeking comment.