TMZ.com reported that Johnson was found dead Monday. Police officers responded to her Los Angeles home around 11:51 a.m. where paramedics had already pronounced Johnson dead, officer Sara Faden said.
Faden said she did not know how long Johnson may have been dead by the time authorities arrived.
She said Johnson's death may have been from natural causes since a preliminary investigation turned up no signs of foul play. But Faden added that a final cause of death will be determined by coroner's officials, who will seek toxicology tests. Results of those tests could take six weeks to obtain.
In a statement released through publicist Jesse Derris, the Johnson family says it "is mourning its tragic loss, and asks for privacy during this very difficult time."
Casey Johnson gained celebrity as the girlfriend of Tila Tequila, a reality TV star best known for "A Shot at Love with Tila Tequila," which ran for two seasons on MTV.
Tequila's publicist says the two were engaged.
On her Twitter page, Tequila wrote, "Everyone please pray 4 my Wifey Casey Johnson. She has passed away. Thank u for all ur love and support but I will be offline to be w family."
Johnson, a high school classmate of fellow socialite Paris Hilton, told Vanity Fair in a 2006 interview that her decision to turn down Hilton's invitation to be her co-star on "The Simple Life" was "the stupidest mistake of my life." Hilton eventually chose Nicole Richie. "I kick myself in the butt everyday," she told the magazine.
