Michael Jackson’s personal doctor who was at his side when he died has had his clinic in Texas raided by federal drug agents and Los Angeles police as part of the ongoing investigation into the pop star’s death.

More than 20 officers in a convoy of up to 15 cars turned up at the Armstrong Medical Clinic in Houston this morning where Conrad Murray has his office. The agents were armed with a search warrant that is reportedly connected to the autopsy on Jackson which found traces of the powerful anaesthetic Propofol.

Murray tended for Jackson after he collapsed in his rented mansin in LA on June 25. The physician tried to resuscitate the singer until paramedics arrived.

A cardiologist, he is based in Las Vegas and also carries permission to treat patients in California, Nevada and Texas. He had been taken on by Jackson to care for him ahead of and during his final tour in London that had been due to start this month.

There has been no suggestion until now that Murray was being considered a suspect in Jackson’s death. The website TMZ which broke the story of the star’s collapse has claimed that his death was being treated as homicide, but that was denied by the LA police.

Murray has been interviewed twice by detectives, and it was revealed earlier today that he has been called back for a further interview later this week at the request of the coroner’s office which is seeking more information.

The inquiry has come to focus on Propofol, which was found in Jackson’s house after he died. It is understood that Jackson requested the drug on occasion to help him sleep, though the anaesthetic is considered very potent and highly dangerous unless administered by a practised medical expert.