Jackson doctor's clinic raided
Murray had been interviewed by police as a witness to the pop star's death, but has not been considered a suspect.
Los Angeles police and agents of the U.S. Drug Enforcement Administration searched the north Houston clinic on Wednesday for about 2½ hours.
Ed Chernoff, Murray's attorney, said in a statement that a search warrant authorized law enforcement to search for and seize items, including documents, which they believed constituted evidence of the offence of manslaughter.
Chernoff said agents left with "a forensic image" of a computer hard drive and 21 documents.
Crowd gathers to watch raid
Houston police surrounded the building as the investigators went inside. DEA spokeswoman Violet Szeleczky said about 20 people were in the Armstrong Medical Clinic, including employees.
A neighbourhood crowd gathered to watch the raid.
Murray has emerged as a central figure in the investigation into Jackson's death on June 25. The doctor, who had been recently hired by Jackson, was with him in his mansion and tried to revive him. He has been interviewed by police, but he had not been considered a suspect in the singer's death.
Chernoff's spokeswoman, Miranda Sevcik, told The Associated Press that Murray's legal team was surprised by the search.
She said the agents were looking for Murray's records, not drugs, but wouldn't specify further. She declined to say how the search related to Jackson's death.
Police also served a subpoena Wednesday at the office of Cherilyn Lee, Jackson's nutritionist.
Although Lee has co-operated with police, a subpoena was necessary because records related to her treatment of Jackson are protected by law, Lee's spokeswoman said.
Medical records sought in California
The attorney posted a statement on his law firm's website late Tuesday saying investigators from the Los Angeles County coroner's office have asked for medical records in addition to those already provided by Murray.
"The coroner wants to clear up the cause of death; we share that goal," Chernoff said in his statement.
"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."
Although Chernoff has said the doctor didn't give the pop star any drugs that contributed to his death, Murray has nonetheless received attention from those angry over the singer's death.
"Dr. Murray was the last doctor standing when Michael Jackson died, and it seems all the fury is directed toward him," Chernoff said.
"Dr. Murray is frustrated by negative and often erroneous media reports. He has to walk around 24-7 with a bodyguard. He can't operate his practice. He can't go to work because he is harassed no matter where he goes."
Anesthetic found in home
Investigators found the powerful anesthetic propofol in Jackson's home, according to a person with knowledge of the investigation. The person is not authorized to speak publicly and requested anonymity.
The officials are working with the Drug Enforcement Administration and the California attorney general's office to determine how the medications got there.
Police detectives have already spoken to Murray twice — once immediately after the singer's death and again two days later. Police investigators say Murray is co-operating in their investigation. The Las Vegas-based doctor is also licensed in California, Nevada and Texas.
A cause of death has yet to be determined for the pop star. The coroner's office is expecting to release autopsy results next week.
Sevcik said the interview with coroner's investigators might happen Friday. Murray is in Las Vegas, where he has a medical office, she said, and Chernoff would be speaking to investigators without the doctor present.