Entertainment Tonight.

The Ronald Reagan UCLA Medical Center is speaking out to ET about attempts to save the late Michael Jackson after the medical emergency that led to his death.

The hospital tells ET it is believed that Jackson suffered cardiac arrest in his home. At the time, Jackson's personal physician tried to revive him, as did the paramedics who rushed the star to the hospital.

The hospital adds that once Jackson arrived at the medical center, a team of doctors, including emergency physicians and cardiologists, unsuccessfully attempted to resuscitate him for more than one hour.

Jackson's cause of death is unknown, pending an autopsy scheduled for Friday.

Related stories on ETonline.com:Britney Spears 'Devastated' by Loss of Michael Jackson
Michael Jackson Autopsy News