Whitney Houston died from a combination of prescription drugs and alcohol, celebrity website TMZ.com reported Monday.
The report quoted family members of the late soul diva, who said that they had been informed of the cause of death by the coroner, dpa reported.
Houston died Saturday in a bathtub at the Beverley Hills Hotel at the age of 48. Results of her autopsy are not expected for several weeks until after the results of toxicology tests are available, Los Angeles County Coroner Ed Winter said on Sunday.
Her death cast a dark shadow over the Grammy Awards on Sunday night, which opened with a prayer for the six-time Grammy winner and climaxed with a moving tribute to Houston by Jennifer Hudson, who sang Houston's greatest hit, I Will Always Love You.
British singer Adele won six Grammys, including Album of the Year, in one of the most dominant displays by a female vocalist since Houston was at the height of her stardom.
Houston's body is expected to be flown from Los Angeles to Atlanta on Monday. Her daughter Bobbi Kristina, 18, was rushed to hospital on Sunday morning suffering from anxiety, but was released later in the day, local broadcaster KCBS reported.
Houston was one of the world's biggest stars for a decade starting from the mid 1980's, racking up strings of top-selling singles and albums, as well as the hit movies The Bodyguard and Waiting to Exhale.
Hailed as having one of the best voices in pop history, her good-girl image made her one of America's best-loved personalities.
But her career and image went rapidly downhill as she struggled with addictions to drugs and alcohol. An attempted comeback in 2009 faltered when it became clear that her once-powerful voice had become hoarse and raspy after years of substance abuse.
According to her website, Houston sold more than 170 million combined album, singles and videos worldwide.
She grew up in Newark, New Jersey. Her mother Cissy Houston was a gospel singer and her cousin was music great Dionne Warwick.