Los Angeles detectives, federal drug agents and Houston police raided the offices of Dr. Conrad Murray, the physician who was with Michael Jackson when the entertainer was stricken at home last month.

Acting on a search warrant, a caravan of 15 cars descended on the clinic at about 10:20 a.m. Wednesday, with officers in Drug Enforcement Administration windbreakers seen entering the building.

Agents are focusing the investigation on the drug Propofol, the powerful anesthesia that Jackson may have taken before his death, a law enforcement source tells People.

“It is Conrad Murray they’re looking at,” the source says. “They are looking for Propofol, along with anything else they find. But Propofol is the big one.

Murray has already been interviewed by police and through his attorney has denied wrongdoing.

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