Police have drafted in officials from the Drug Enforcement Administration as they investigate the cause of Michael Jackson's sudden death.

The federal agency will provide expertise in investigating claims that Jackson abused prescription drugs and may have been taking a dangerous sedative used in hospital operating rooms to induce unconsciousness.

DEA officials have powers to investigate Jackson's doctors and the sources of the drugs provided to the pop singer.

Jackson admitted in testimony in 2005 that he had been addicted to prescription drugs, including painkillers and anti-depressants. Persistent reports have claimed that he continued to take them. TMZ.com, a celebrity gossip website that broke the news of Jackson's death, claimed that Jackson used a number of aliases to order drugs from pharmacies.

A Beverley Hills pharmacy filed a lawsuit against Jackson in 2007 claiming he ordered medicines worth $100,000 in just two years. The lawsuit was settled.

Cherilyn Lee, a registered nurse whose specialty includes nutritional counseling, said Jackson pleaded with her to provide Diprivan, an intravenous anesthetic drug also known as Propofol, in recent months because he was suffering from crippling insomnia.

Today his British former bodyguard claimed blamed the singer's death a week ago on doctors who had supplied him with unnecessary medication, claiming they had "blood on their hands".

Matt Fiddes, 30, from Barnstaple, Devon, who was introduced to the pop star around 10 years ago by psychic Uri Geller, described how he and Mr Geller tried to hide drugs and syringes from Jackson.

Mr Fiddes said: "I never witnessed him actually taking drugs but I knew they were there and I confiscated packages, and Uri did too. And Uri confiscated injection equipment from his room ... Uri would scream at Michael, you know, intensely, to stop doing this but we were getting pushed out," he told Sky News.

The LA coroner's office performed an autopsy on the 50-year-old singer's body on Friday but deferred a decision on the cause of death, ordering toxicology tests. A second, private autopsy has been requested by the family, over concern about his final hours. The Jackson family has questioned the role of the singer’s physician, Conrad Murray, who was with him when he collapsed.

A memorial service for Michael Jackson is now likely to take place in Los Angeles, it emerged last night, after the family ruled out a public wake at the star’s Neverland ranch.

It is thought that the logistics of handling tens of thousands of mourners at the remote estate in rural Santa Barbara County, 130 miles from Los Angeles, proved too complicated. A permit for a burial at the site could also not be issued in time.

Reports of a lying-in-state for Jackson at Neverland surfaced on Tuesday as estate staff began preparations. Last night a spokesman for the Jackson family said that there were no plans for private or public services at the estate but that plans for a public memorial would be announced soon. These could take place at the 20,000-seat Staples Center or the bigger Los Angeles Coliseum, the main venue for the 1984 Olympic Games.

Michael Jackson’s will, made seven years ago, gives his estate to a family trust for his children and names his mother as their guardian. His former wife, Debbie Rowe, is cut out of the will, as is his father, Joe

The will names Diana Ross, 65, the singer and lifelong friend of Jackson, as a guardian to the children if his mother, Katherine Jackson, 79, is unable to take up the role. Katherine Jackson has already been granted temporary guardianship by a judge.

The document, filed in court in Los Angeles and dated July 7, 2002, gives his estate to the Michael Jackson Family Trust, formed in 2002, and puts a value on the estate of $500 million.

John Branca, Jackson’s lawyer, and John McClain, a music executive and a family friend, were named as co-executors of the will. The naming of the co-executors sets up a potential clash with the family over Jackson's financial affairs. Control of the trust to handle his estate goes to Mr Branca and Mr McClain.

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