A lawyer for Dr. Conrad Murray's, Edward Chernoff, said in a statement that officials were searching the office for evidence of "the offense of manslaughter."
"We reviewed the warrant and remained on the premises while the search was being executed. The search was conducted by members of the DEA, two Robbery-Homicide detectives from the Los Angeles Police Department and Houston Police officers," Chernoff said.
"The search warrant authorized law enforcement to search for and seize items, including documents, they believed constituted evidence of the offense of manslaughter," he said.
Two dozen DEA agents, Los Angeles police detectives and Houston officers swarmed the office building where Dr. Conrad Murray works, ABC News reported.
The agents had obtained a search warrant for the raid based on the preliminary autopsy findings, which linked Jackson's death to the powerful drug Propofol, according to ABC affiliate KTRK-TV in Houston.
Los Angeles police and federal Drug Enforcement Administration agents carried away five or six plastic storage containers and several thick manila envelopes after a three hour-search of Murray's sprawling home in a gated Las Vegas community.
Across town, authorities searched his medical offices, Global Cardiovascular Associates Inc., for nine hours seeking documents. Investigators removed several boxes but declined to describe what they had seized.
Last week, authorities searched Murray's clinic and storage unit in Houston.
Murray was the last doctor to see Jackson alive and tried to revive him after finding him unconscious in the singer's rented Holmby Hills mansion.
"Dr. Murray's legal team is looking into the matter," Murray's spokesman said today after the raid began.
An attorney for the doctor said he didn't give the King of Pop any drugs that contributed to his death.
Only hours after the Houston raid Los Angeles County Coroner's officials were at the Inglewood office of Cherilyn Lee, Jackson's former nutritionist serving a subpoena for records related to her treatment of Jackson, Lee's spokeswoman said.
Belinda Foster says Lee is cooperating with investigators but required a subpoena because the records were protected by law. Lee treated Jackson between January and April, when she says he began persistently asking her for the powerful anesthetic central to the death investigation.
The singer's body has undergone two autopsies -- one conducted by the Los Angeles County Coroner's office and a second done privately at the family's request -- and findings in both were "consistent," according to E! News.
The private autopsy, reported today, showed the singer had needle marks and traces of Propofol, according to source familiar with the post-mortem examination told E! News.
Both investigations found the Propofol, which is administered through IV, in the singer's system and discovered in the Holmby Hills mansion where he had a cardiac arrest, according to E! News.
The county coroner's report was inconclusive and the cause of death could not be determined until the toxicology tests come back in six to eight weeks.
There were no signs of foul play or trauma, according to the first autopsy.
The private autopsy was given on June 27, a day after the coroner examined the body.
Jackson was on prescription medication when he died, county officials said, but the full report on his death won't likely be available until at least next week because of the ongoing investigation into his death.