So many millions of fans tried to register for free tickets to a Michael Jackson memorial service in Los Angeles that they brought down the organiser’s website, as squabbles continued over custody of the star’s children and more evidence of drug abuse emerged.

The service will take place at the Staples Center, in downtown Los Angeles, after a funeral attended by family and close friends. The centre, which seats 20,000, was used by Jackson in the days before his death to rehearse for a run of 50 shows in London that had been due to start this month.

Fans have until 6pm today to register for the service on the website staplescenter.com . A lottery will decide who will qualify for the 17,500 tickets on offer, which will be allocated in pairs to US residents. The Jackson family said the website received more than half a billion hits by yesterday morning, causing the site to crash.

The service will be shown live on television and police and organisers warned all those without tickets to stay away. Assistant Police Chief Earl Paysinger said that anywhere from 250,000 to 700,000 people could try to reach the arena, even though a wide area around the Staples Center will be sealed off.

A spokesman for the Jackson family declined to comment on whether Debbie Rowe, Jackson’s former wife and mother of his two eldest children, would attend the private funeral. She is considering contesting custody of the children, who have been put under the temporary custody of the singer’s mother, Katherine. A court hearing has been put back to July 13.

Ms Rowe told a TV news reporter that she wanted to keep Jackson’s father, Joe, away from his grandchildren. He has admitted whipping his children with a belt when they were young. He is still married to Katherine, though the couple are separated.

Further details emerged yesterday of Jackson’s alleged abuse of painkillers and other prescription drugs. The powerful sedative Diprivan was found in the rented mansion in Los Angeles where he died. The discovery reinforces claims from a nutritionist treating Jackson that he claimed to have been given a powerful sedative for insomnia before his death.

Cherilyn Lee said she repeatedly rejected his demands for the drug, which is used in operating theatres and is given intravenously. The drug has a very narrow therapeutic window, meaning doses not much larger than the medically recommended amount can stop a person’s breathing, leading to cardiac arrest.

The Los Angeles coroner’s office performed an autopsy on Friday but deferred a decision on the cause of death, ordering toxicology tests. A second private autopsy has been requested by the family.

AEG, which runs the Staples Center, plans to release a DVD taken from 100 hours of footage of rehearsals for the planned shows in London. It is expected that Jackson will be buried at Forest Lawn Memorial Park. The family had hoped to bury him at the Neverland ranch but had difficulties in obtaining a permit.

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