LOS ANGELES: Investigators looking into the death of pop star Michael Jackson have seized new information to analyse as they narrow their focus in what could become a criminal investigation.

Almost one month after the King of Pop died, federal and local agents 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 offence 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.

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 on Friday 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 towards him.” Murray also has a clinic in Las Vegas, which showed no signs of activity on Wednesday.

Also 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 cooperating with investigators but required a subpoena because the records were protected by law, Foster said.