The home of Michael Jackson's doctor, Conrad Murray, was searched by federal investigators yesterday following claims he gave the singer a powerful anaesthetic hours before he died.
Officials, believed to be from the Drug Enforcement Agency, were seen entering Dr Murray's home and office in Las Vegas.
The search comes after reports that police believe Dr Murray gave the pop star propofol, a clinical anaesthetic, to make him sleep shortly before he died.
Officers are working on the theory that the powerful sedative caused his heart to stop.
Yesterday's raid followed that on Dr Murray's clinic in Houston, Texas, last week.
On that occasion, agents spent two-and-a-half hours at the site, leaving with 21 documents and a “forensic image” of a computer hard drive.
The investigation is increasingly being focused on the role of Dr Murray, Jackson's personal physician who was with him when he died.
The doctor has been quizzed twice by police in Los Angeles as part of their probe, with a third interview planned.
He has not been named as a suspect, but court records have identified the 51-year-old physician as the subject of a manslaughter investigation.
Yesterday, an official told the Associated Press that Jackson enlisted a number of doctors — including Dr Murray — to administer propofol via a drip.
The law enforcement source, who spoke on the condition of anonymity, added that on June 25, the day the singer died, Dr Murray gave him the drug sometime after midnight.
The drug he allegedly administered, propofol, lowers the recipient’s heart rate and blood pressure. It is usually only used in hospitals because of the risks involved.
A safety warning on the drug's label states that the patient must be monitored at all times.
Furthermore, equipment to aid breathing and provide artificial ventilation and oxygen “must be immediately available”.
Dr Murray's lawyer Ed Chernoff has publicly stated that his client “didn't prescribe or administer anything that should have killed Michael Jackson”.
Asked about the latest allegations over propofol, Mr Chernoff said: “We will not be commenting on rumours, innuendo or unnamed sources.”