The man at the centre of the investigation into Michael Jackson's death has broken his silence to thank supporters and assure them he had told the truth.

Dr Conrad Murray posted a short video message on YouTube as police continue to focus on his role in the death of the late pop star.

Message: Dr Murray told his supporters not to worry

Federal agents are believed to be working on the theory that Dr Murray administered a powerful sedative of the type thought to have killed Jackson shortly before he collapsed in his rented Beverly Hills home.

Over the last month, two offices connected to Dr Murray have been searched by police, as has his home.

Last week officials from the Drug Enforcement Administration walked away from a raided Las Vegas pharmacy with evidence that showed Jackson's personal physician purchased propofol - the anaesthetic thought to have caused his heart to stop beating.

The pop star died on June 25 at the age of 50. Dr Murray was at his side when he died.

Since then, Dr Murray has been interviewed twice by officers involved in the case.

The doctor has not been named as an official suspect, but court records have identified the 51-year-old physician as the subject of a manslaughter investigations.

Yesterday, it was disclosed that Jackson's mother is considering filing a wrongful death lawsuit over the circumstances surrounding her son's death.

Burt Levitch, a lawyer for Katherine Jackson, said the idea had "been floated" and the main name that had been mentioned was Dr Murray.

To date, Dr Murray has kept away from speaking in public, with statements being made through his lawyer.

But he issued a direct message to supporters via YouTube thanking friends and patients for letters of support.

Dr Murray said: "Your messages give me strength and courage and keep me going. They mean the world to me.

"Please don't worry, as long as I keep God in my heart and you in my life I will be fine.

"I have done all I can do. I told the truth and I have faith that truth will prevail."