Chyna, who rose to fame as a wrestler and actress, was found dead Wednesday in her Redondo Beach home, authorities said.
Anthony Anzaldo, her business manager, said she was found in her Redondo Beach apartment in the afternoon. She was 46.
Ed Winter, a spokesman for the Los Angeles County coroner's office, said police initially reported the death as a "possible overdose or natural death." An autopsy is pending.
Redondo Beach police said officers found Chyna, whose real name was Joan Marie Laurer, dead on her bed, after receiving a call from her friend about a woman not breathing. The friend said Chyna had not answered her phone in a few days, according to a Redondo Beach Police Department statement.
There were no obvious signs of foul play, Redondo Beach police Lt. Todd Heywood said.
"From the preliminary investigation, it appears that the deceased passed away prior to being discovered by the friend," the police statement said.
Chyna was a star in World Wrestling Entertainment beginning in the mid-1990s. She billed herself as the "9th Wonder of the World" because her wrestling predecessor Andre the Giant had already called himself the eighth. She was a member of the wrestling squad that dubbed itself "D-Generation X," often wrestled against men and at one point was the WWE women's champion.
Chyna also performed as an actor in adult entertainment and mainstream films. For a time, Chyna was a big name in popular culture. "If They Only Knew," her autobiography, reached the New York Times bestseller list in 2001.
Chyna was a native of Rochester, N.Y., and graduated from the University of Tampa in Florida before taking up wrestling.
She joins a long list of WWE professional wrestlers who have died relatively young, including Rick Rude, Curt "Mr. Perfect" Hennig, the Ultimate Warrior and Owen Hart.
After leaving the WWE in 2001, she posed for Playboy and appeared in adult films and on reality TV, including the shows "The Surreal Life" and "Celebrity Rehab with Dr. Drew."
More recently, she moved to Japan and for a while taught English.
People in the world of wrestling expressed shock and sadness over her death.
"She was truly a pioneer in our industry, and she will be missed," WWE official Stephanie McMahon said on Twitter.
"Devastated over Chyna's passing," wrote Hulk Hogan on Twitter. "Such a beautiful soul and so kind to my children."
In Redondo Beach on Thursday, Connie Clark said she lived in the same Esplanade Street apartment building as Chyna and had just waved to the wrestler a few days ago, when Chyna was working out on her balcony.
Clark said Chyna had moved into the building about six months ago, and when the women first met, she introduced herself as "Chyna" while Clark was outside feeding the birds.
Clark initially misunderstood and thought she was talking about visiting China.
"She said, 'No, no, no, my name is Chyna," Clark said. "She said, 'Well, Google me. You may not like what you find.'"
The women would talk and trade stories. Clark lived a floor below Chyna, and they would take the same elevator. Clark said she accidentally ended up on Chyna's floor on Wednesday and saw detectives, who told her there had been a death.
"She was just very, very nice," Clark said. "It's a sad situation.... She was a health nut on one side, and then on the other side she had her demons. I think the demons [are] what got her."
Robert Hawkinson, 50, rode his bike by the apartment building, trying to see where she lived. Hawkinson said he had followed her career, watching her wrestle with WWE. The news of her death didn't surprise him.
"You heard stories about her having issues," he said, adding that "she didn't know how to make herself happy, it seemed like."
Linda Evans, who lives in the apartment building, said she was cooking dinner when she heard sirens Wednesday. Evans said she lived in the building for almost two years and saw Chyna from time to time in the elevator, and that they would say hello.
Evans said she didn't know who Chyna was at the time. People in the building are very quiet, she said.
Joyce Sun Marsh, who said she used to work for a graphic design company that designed the packages for Chyna's dolls years ago, called the wrestler's death "really sad."
"Back in the day, she was a huge wrestling star, back when the Rock was still the Rock," Marsh said while walking along Esplanade with a friend. "Chyna was a big deal way back when."
Marsh said she never met Chyna personally and didn't know that the celebrity had lived in the area.
"Definitely too early," Marsh said of her death.