"I can confirm that Whitney Houston was pronounced dead at 3:55 p.m. at the Beverly Hilton Hotel," Beverly Hills police Lt. Mark Rosen told People.com.
"We received a call at 3:43 p.m. from hotel security and Beverly Hills Fire and police responded minutes later. It's unclear who notified hotel staff because she has quite an entourage here at the hotel. We attempted to resuscitate her, to no avail."
Asked if there was reason to suspect drugs or foul play, Rosen said, "We don't know yet, her death is under investigation."
Houston publicist Kristen Foster also had confirmed Houston had passed.
The Los Angeles Times reported Houston's death brought a quick outpouring from other entertainment stars.
Russell Simmons said he was "deeply saddened by the death of Whitney Houston...may she rest in peace."
"Just heard the news. so crazy," Justin Bieber said in a Twitter post. "One of the GREATEST VOICES EVER just passed. RIP Whitney Houston."
"Wow. RIP Whitney Houston. Grew up on her," actress Elizabeth Banks said. "She contributed to the soundtrack of many of my 12-year old sleepover parties."
Author Jackie Collins called her "a beautiful & talented woman."
Writer Jordan Bach wrote, "May the wings of angels encircle Whitney Houston. Gratitude for her gifts, sorrow for her agony, and prayers for her release at last."
The Hollywood Reporter said Houston, whose career was dogged by reports of drug use, stints in rehab centers and other personal problems, was to have appeared at the Clive Davis pre-Grammy gala Saturday night.
The entertainment industry newspaper said she allegedly was overheard dressing down an assistant in the Beverly Hilton Hotel Thursday morning and that night allegedly got into an altercation with "X Factor" finalist Stacy Francis at an R&B appreciation event where she was described as "belligerent," the Reporter said.
Her publicist had previously said Houston, who had been considered for a judges' seat on "X Factor," was at a spa Friday.
A source close to Clive Davis was quoted by the newspaper as saying, "This is a sad day and it will be a sad Grammys weekend."
The Newark, N.J., native was known for such songs as "Saving All My Love for You," "How Will I Know," "Greatest Love of All" and "I Wanna Dance with Somebody (Who Loves Me)."
Her movie credits included "The Body Guard," "Waiting to Exhale" and "The Preacher's Wife."
She had a tumultuous marriage to singer Bobby Brown, with whom she had a daughter Bobbi Kristina Houston Brown. They divorced in 2007, People said.