Federal authorities have raided the Houston office of Dr. Conrad Murray, the physician who was with Michael Jackson when the singer died at home last month.

According to multiple sources, federal Drug Enforcement Agents — working with the Houston police and Los Angeles detectives — arrived in a 15-car caravan at Murray's Armstrong Medical Clinic at approximately 10:20 a.m. CT, acting on a search warrant.

The focus of that warrant, according to sources quoted by People, was the drug Propofol, the powerful anesthesia that Jackson might have taken before his death.TMZ reported that the agents were looking for "all medical records relating to Michael Jackson."

Murray's attorney, Edward Chernoff, sent TMZ a statement regarding the search, telling the Web site, "The coroner wants to clear up the cause of death; we share that goal. 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."

Late last month, Murray met with LAPD detectives for three hours to answer questions about Jackson's death. Detectives also impounded Murray's car, which was parked at Jackson's home, because it could contain evidence related to the singer's death. They also served search warrants to three different physicians.

In early July, Cherilyn Lee, a registered nurse and nutritional counselor, told The Associated Press that Jackson had begged her for Diprivan — also known as Propofol — but that she denied his requests because it could be harmful to his health.

TMZ has reported that Propofol was found at Jackson's house. The drug is extremely potent — it is give intravenously as a general anesthetic used to sedate patients for surgery — and is only available to medical personnel.