Police want to question 30 doctors, nurses and chemists who may have helped to supply Michael Jackson with prescription drugs as his family argue over the final details for his memorial service, which is to be held on Tuesday.

The police taskforce, established as a “formality” when Jackson died 10 days ago, is snowballing into a widespread investigation checking prescriptions for painkillers found in his house under fictional names such as Jack London and Omar Arnold.

Omar was Jackson’s nickname for Lou Ferrigno, the 1970s Hulk actor who was training Jackson for his 50 London shows. Arnold is the first name of his dermatologist, Arnold Klein, who was reportedly preparing his skin for the same performances.

Klein, who denies any wrongdoing, is on a list of people who police and drug enforcement officials want to interview.

Others include Jackson’s live-in doctor, Conrad Murray, a cardiologist who has talked to the police twice, and Cheri-lyn Lee, his last nurse. She said Jackson had begged her for diprivan, a milk-like anaesthetic also known as propofol and used to sedate horses.

Police have confirmed that the anaesthetic was found in Jackson’s home but refused to comment on reports that he had taken it through an IV drip which was set up in his bedroom hours before he suffered a cardiac arrest.

Drew Pinsky, a Los Angeles doctor who has treated hundreds of drug addicts, including many showbusiness celebrities, said it was known that Jackson was addicted to painkillers such as demerol. However, talk of insomnia and night sweats suggested he may have been trying to break his dependency before his “come-back” shows in London.

“Cleaning his system out could have made him vulnerable to one last dose of demerol or diprivan,” said Pinsky.

Identifying what killed the 50-year-old star still haunts the Jackson family. Jermaine Jackson said he would be “hurt” if toxicology tests found drugs in his younger brother’s system. His father Joseph, 79, wanted to delay the funeral until the forensic tests were finished.

There have been other divisions as the family prepare for the memorial service at the Staples Center, a sports arena in downtown Los Angeles.

They were still debating this weekend whether his body, housed in a $25,000 gold-plated coffin, would be present at the service, which could include President Barack Obama among the guests.

Jermaine Jackson is believed to have argued for an open casket to show that his brother was outwardly healthy when he died, but their mother Katherine regarded it as undignified. She has favoured placing Jackson’s signature single glove on top of the coffin.

Up to 17,500 “guests” will learn today if they have been selected by lottery to attend the memorial service, which will feature live and filmed tributes. More than 500,000 have applied.

The service, described as a “celebration”, will be beamed across the world via television networks and the internet. Police are bracing themselves for crowds of up to 700,000 trying to reach the Staples Center which is owned by AEG Live, the same entertainment group which was hosting the doomed concerts at the O2 The planned series of 50 concerts for 800,000 people had generated about £52m in ticket sales. AEG faced having to pay a full refund until it hit on the idea of offering people their tickets, which feature a holo-gram of Jackson, as a “souvenir”. It claims that half those buying tickets have already accepted.

The company, which had paid £15m as an advance to Jackson and in other costs, is also claiming copyright on 100 hours of film footage of the singer shot on 3-D cameras in rehearsal, which may be released as a film in cinemas.

It will lose a £10m Lloyd’s insurance payout if it is found that the singer died of natural causes. He was covered only for accidental death but that does include an unintentional drugs overdose.

Explore Music

• CD Reviews

• Live Reviews

• Classical

Editor's choice

• The 100 Best Films of the Decade
• 70 facts you didn't know about Marvel
• The 50 Biggest Movies Of 2010