Coroner's officials said they also found traces of marijuana, Xanax and benadryl in her system.

Houston died just hours before she was scheduled to appear at producer Clive Davis' pre-Grammy Awards bash.

The singer was buried in a New Jersey cemetery next to her father after an emotional four-hour funeral service that was attended by friends, family and superstars such as Oprah Winfrey, Tyler Perry, Alicia Keys, Mariah Carey, Mary J. Blige, Jennifer Hudson and Roberta Flack

Houston, a sensation from her first, eponymous album in 1985, was one of the world's best-selling artists from the mid-1980s to the late 1990s, turning out such hits as "I Wanna Dance With Somebody", "How Will I Know", "The Greatest Love of All" and "I Will Always Love You". But as she struggled with drugs, her majestic voice became raspy, and she couldn't hit the high notes.

Interest in her music has skyrocketed since her death, pushing her songs back on to charts and into heavy rotation on the radio.

Singer Whitney Houston accepts the International Artist of the Year award at the 2009 American Music Awards in Los Angeles, California in this November 22, 2009 file photo. [Photo/Agencies]