Investigators have conducted post-mortem tests on the body of Rodney King, the central figure of the deadly Los Angeles riots, but it was expected to take several weeks to determine what killed him, officials said.
Coroner's officials will await results from toxicology tests that could take up to six weeks to gather before determining how Mr King died.
He was pulled from the deep end of his pool early on Sunday by police who were called to his home by his fiancee.
Mr King, 47, became famous after he was severely beaten by Los Angeles police in 1991. The beating was captured on videotape and broadcast worldwide, as were photos of Mr King's bloodied and bruised face.
The baton blows and kicks inflicted by officers left Mr King with 11 skull fractures, a broken eye socket and facial nerve damage.
The trial of four officers charged with felony assault ended after a jury with no black members acquitted three of the officers on state charges; a mistrial was declared for a fourth. The verdict sparked one of the most costly and deadly race riots in US history.
Rialto Police are investigating Mr King's death as an apparent drowning and said they have found no signs of foul play. Mr King's fiancee spoke to police for several hours on Sunday and is considered a witness in the case, Rialto Police Officer David Shepherd said.
A police officer remained stationed outside Mr King's single-storey home on Monday, with several news crews also remaining in the neighbourhood. Cars slowed to look at the house, and some stopped for passengers to snap photos. But no memorial to Mr King had been created at the residence.
Toxicology results will show whether Mr King, who struggled with addiction throughout his life, had any alcohol or drugs in his system.
Police have said there were no signs of alcohol or drug paraphernalia near the pool. Officers were seen taking a marijuana plant out of the house on Sunday, but Mr Shepherd said he could not confirm what items were taken from the home.