Michael Jackson, the king of pop, has died at the age of 50, after suffering a cardiac arrest at his home in Beverly Hills. Pop star Madonna said: "The world has lost one of its greats, but his music will live on forever."
Fans gathered outside the clinic where he was pronounced dead on Thursday. A post-mortem is taking place on Friday.
Family lawyer Brian Oxman told US TV that he had been concerned about the star's use of pain relief medication. Mr Oxman said that Jackson took prescription pain relief for injuries sustained earlier in his career, including bones broken in a stage fall.
"It caused him great pain. He just didn't like to feel such discomfort. He started taking pain medication. It became part of his life."
US authorities have said final results of the post-mortem could take up to eight weeks while toxicology tests are completed.

Paying tribute to the star, musician Sir Paul McCartney said: "I feel privileged to have hung out and worked with Michael. He was a massively talented boy-man with a gentle soul."
The singer's ex-wife Lisa Marie Presley said she was "sad and confused". "This is such a massive loss on so many levels, words fail me."
Pop star Justin Timberlake, who has been compared to Jackson, said: "We have lost a genius and a true ambassador of, not only pop music, but of all music."
The musician added: "He has been an inspiration to multiple generations."
Paramedics were called to the singer's Beverly Hills home at about midday on Thursday after he stopped breathing.
He was pronounced dead two hours later at the UCLA medical centre in west Hollywood. Jackson's brother, Jermaine, said he was believed to have suffered a cardiac arrest.
Watch one of his best video clips: