Rodney King speaks during a signing of his book " The Riot Within: My Journey from Rebellion to Redemption " in New York in this April 24, 2012 file photo.

Rodney King, whose beating by police in 1992 sparked one of the worst urban riots in US history, died of accidental drowning fuelled by drugs and alcohol, a coroner's report said on Thursday.

The 47-year-old was in a “state of drug- and alcohol-induced delirium” when he fell or jumped to his death in the backyard swimming pool of his home in Rialto, east of Los Angeles early on June 17. He was found by his fiancee Cynthia Kelly.

King was said to be smoking marijuana and drinking in the hours before his death, according to San Bernadino County officials cited in a coroner's report that listed his death as an accident.

The drugs and alcohol together compounded the effect of a heart condition, probably leading to cardiac arrhythmia. “Thus incapacitated, (King) was unable to save himself and drowned,” said the report, cited by local media including the Los Angeles Times.

Kelly called 911 shortly before 5:30 am, and told police that King had been pounding on a sliding glass door outside the house, waking her up a short time earlier.

“She described him making grunting and growling sounds and having frothy secretions coming from his mouth,” the report said, adding that King was wearing “his underwear down around his knees.

He then “apparently fell backwards onto the planter just east of the sliding glass door,” it said, adding that when Kelly went to find her cellphone to call 911, she heard a splash.

Going outside, she saw him at the bottom of the pool. A poor swimmer, she tried to wake King up by prodding at him with a pitchfork and hoe, the report said.

Traces of cocaine, marijuana and phencyclidine (PCP) were found in his blood system, along with alcohol. A spokeswoman for the San Bernardino coroner's office could not confirm details of the report.

In 1991, King was severely beaten by four white police officers who struck him more than 50 times with their wooden batons and used a stun gun following a high-speed car chase.

The officers went on trial for use of excessive force but were acquitted on April 29, 1992, triggering days of deadly rioting in Los Angeles that left more than 50 people dead and caused around a billion dollars in damage. - AFP