Michael Jackson's family and close friends held a private service at a Los Angeles cemetery on Tuesday as fans crowded into the city's downtown area for a star-packed public memorial to the King of Pop.

Singers Mariah Carey, Usher and Jennifer Hudson will mix with R&B veterans Smokey Robinson, Lionel Richie and Stevie Wonder while sports stars like Kobe Bryant and other celebrities were expected at the public farewell to the singer who died suddenly on June 25.

A fleet of black vehicles took Jackson's parents and siblings to the cemetery. The gold-trimmed casket was later carried off in a hearse to the Staples Center sports arena where the memorial show was being held.

Some 18,000 fans and friends have tickets for the Staples Center event and a nearby, overflow theater for a two-hour ceremony.

Jackson, 50, died after suffering cardiac arrest in his rented Los Angeles mansion during rehearsals for a 50-show series of comeback concerts in London after a fallow period in his singing career.

Police estimate more than 250,000 people would gather outside the arena to say farewell to the Thriller singer and one-time member of Motown legends the Jackson 5, who was 50 years-old when he died.

Outside the Staples Center, fans crowded the sidewalks and vendors sold King of Pop t-shirts for $10, as well as posters, necklaces and white sequined gloves that became Jackson's trademark.

MOMENTOUS OCCASION

This is certainly a momentous occasion that is probably as big, if not bigger than, when Elvis (Presley) passed away, said Steve Howard, a resident of Glendale, California, who won a ticket in an online lottery.

The impact he had on American music and world music crossed all boundaries, said Howard.

Tuesday's memorial will focus on Jackson's immense musical achievements, which largely preceded a darker side of the singer's life, including his humiliating 2005 trial and acquittal on charges of child sex abuse.

Questions persist over the cause of his death, which is being investigated by coroners, police and drug police amid reports of possible prescription medication abuse.

Custody of his three children is temporarily in the hands of his mother Katherine but Jackson's ex-wife Debbie Rowe has not yet decided whether to seek custody herself.

Police, security, escorts and sanitation for the memorial ceremony are expected to cost cash-strapped Los Angeles city council nearly $4 million. The city council on Tuesday launched a web site asking for fans to make donations toward the cost of hosting Tuesday's events.

About 1.6 million people registered to be among the 8,750 who won two free tickets to the event, and police expect many who did not win tickets to show up outside.

The memorial was being shown live on U.S. television networks, in some 37 U.S. movie theaters, and was streamed on the Internet.

California