Pop star Michael Jackson has been rushed to hospital in Los Angeles after suffering a suspected cardiac arrest.
The singer was not breathing when paramedics arrived at his Bel Air home at about 1230 (1930GMT), media reports say.
Unconfirmed reports on TMZ website and in the Los Angeles Times say the 50-year-old star has died.
The paramedics performed CPR on Jackson as the ambulance took him to the UCLA medical centre, officials say.
Crowds have begun to gather outside the facility, whose emergency centre has been roped off by police.
The star was due to begin a series of comeback concerts with an appearance at London's O2 arena on 13 July.
He has a history of health problems and has not completed a concert tour in 12 years.
Jackson began his career as a child in family group The Jackson 5.
He then went on to achieve global fame as a solo artist with smash hits such as "Thriller" and "Bad".
But the singer has been dogged by controversy and money trouble in recent years, becoming a virtual recluse.