Pop legend Michael Jackson is reported to have died of a heart attack after he was rushed to hospital in Los Angeles.
Jackson suffered a cardiac arrest earlier today, according to CNN and entertainment news website TMZ.com.
TMZ is now reporting he has died.
"We've just learned Michael Jackson has died," TMZ said.
"Michael suffered a cardiac arrest earlier this afternoon and paramedics were unable to revive him.
"We're told when paramedics arrived Jackson had no pulse and they never got a pulse back," the entertainment website said.
There has been no official confirmation of the reported death and spokespersons for Jackson could not be reached for comment.
Earlier, The LA Times reported paramedics went to the singer's home and found him not breathing.
The newspaper said paramedics performed cardiopulmonary resuscitation at the scene before taking him to the UCLA Medical Centre hospital.
Jackson had been due to start a series of comeback concerts in London on July 13 running until March 2010.
He had been rehearsing in the Los Angeles area for the past two months.
The shows for the 50 London concerts sold out within hours of going on sale earlier this year.
Jackson started out as a child star in the band The Jackson 5 more than 40 years ago.
He has lived as a virtual recluse since his acquittal in 2005 on charges of child molestation.
There have been concerns about Jackson's health in recent years but the promoters of the London concerts, AEG Live, said in March that Jackson had passed a four-and-a-half hour physical examination with independent doctors.