Results from toxicology tests could as long as six weeks to gather before coroner's officials can determine how Rodney King died.
King was pulled from the deep end of his pool early Sunday by police who were called to his home by his fiancee. Investigators conducted an autopsy on his body on Monday.
King 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 King's bloodied and bruised face. The more than 50 baton blows and kicks inflicted by officers left King with 11 skull fractures, a broken eye socket and facial nerve damage.
The trial of four officers charged with felony assault in the beating 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 the nation's history.
Rialto police are investigating the 47-year-old King's death as an apparent drowning and said they have found no signs of foul play. King's fiancee spoke with police for several hours Sunday and is considered a witness in the case, Rialto Police Officer David Shepherd said Monday.
An officer remained stationed outside King's one-story home throughout Monday, with several news crews also remaining in the neighborhood. Cars slowed to look at the house, and some stopped for passengers to snap photos. But no memorial to King had been created at the residence.
Toxicology results will show whether 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 Sunday, but Shepherd said he could not confirm what items were taken from the home.
Lawrence Spagnola, who helped King write his memoir "The Riot Within: From Rebellion to Redemption," said King was proud of the book and hoped it signaled a new chapter in his life where he wouldn't just be remembered as a beating victim.
"Rodney was tired of being the Rodney who was always asked about the beating and if he'd forgiven the cops," Spagnola said. King was happiest when he was outdoors and the two men talked about meeting for a fishing trip, Spagnola said.
"There was a lot of good in him," he said.
He said King seemed like a different person when he spoke about the darker aspects of his life. "When Rodney was talking about spousal abuse or DUIs or drinking, there was a look in his face almost as if he was talking about another person," Spagnola said.
King had plenty to look forward to, including setting a wedding date and the upcoming birth of another grandchild, he said.
Spagnola said King didn't expect he would be remembered, but hoped that his infamous words spoken as the riots still flared, "Can we all get along?" would long outlive him.
Even 20 years after the beating, King still endured migraines, joint pain and other ailments, Spagnola said. Alcohol provided some relief, he said.
"I honestly think he's more at peace now than he ever was in his life," Spagnola said.