Michael Jackson has died in hospital after suffering a suspected heart attack, website TMZ has reported.
Jackson, 50, suffered a heart attack just after 12.00pm local time (19.00pm GMT) and paramedics were unable to revive him, TMZ.comsaid.
When paramedics arrived at his house he was not breathing, LA fire department captain Steve Ruda told the LA Times newspaper.
Jackson was given CPR by fire department paramedics as he was taken to UCLA Medical Center, the LA Times said.
His manager was not immediately available for comment.
Officials at UCLA Medical Center where Jackson was treated could also not be reached.
***'s US correspondent Greg Milam said: "Clearly he was very seriously ill - we can gather that from what his father and other family members said.
"One member of the family had told the TMZ website that Michael is in "really bad shape" and that the brothers were heading for the hospital.
"His father said he wasn't sure exactly what was wrong and was waiting to hear back.
"One can only imagine what it could be like for his family in such circumstances."
Jackson had been about to embark on a comeback, performing 50 concerts at London's O2 Arena.
The concerts had been due to start the concerts on July 13.
He had been rehearsing in the Los Angeles area for the London shows, which sold out within hours of within hours of going on sale in March.
Jackson, 50, suffered a heart attack just after 12.00pm local time (19.00pm GMT) and paramedics were unable to revive him, TMZ.comsaid.
When paramedics arrived at his house he was not breathing, LA fire department captain Steve Ruda told the LA Times newspaper.
Jackson was given CPR by fire department paramedics as he was taken to UCLA Medical Center, the LA Times said.
His manager was not immediately available for comment.
Officials at UCLA Medical Center where Jackson was treated could also not be reached.
***'s US correspondent Greg Milam said: "Clearly he was very seriously ill - we can gather that from what his father and other family members said.
"One member of the family had told the TMZ website that Michael is in "really bad shape" and that the brothers were heading for the hospital.
"His father said he wasn't sure exactly what was wrong and was waiting to hear back.
"One can only imagine what it could be like for his family in such circumstances."
Jackson had been about to embark on a comeback, performing 50 concerts at London's O2 Arena.
The concerts had been due to start the concerts on July 13.
He had been rehearsing in the Los Angeles area for the London shows, which sold out within hours of within hours of going on sale in March.
