The singer, who died nearly three months ago, complained of a sort throat before an assistant suggested she took a bath before attending a pre-Grammy Awards gala.
When the assistant returned, Houston, 48, had drowned.
Investigators who scoured the room say they later found a rolled-up piece of paper, a “spoon with a white crystal like substance on it” and a white powdery substance in a drawer and on a mirror.
Toxicology tests discovered that Houston had cocaine in her heart and extremities.
Coroners officials also noted signs of chronic and recent use of cocaine, including holes in the singer’s nose.
The singer – one of the world’s best known through the 1980s and 1990s – had a long battle with drug addiction.
Houston went into rehab in May 2011 but she was reportedly seen drinking heavily and behaving erratically in the days leading up to her death.
Beverly Hills police Lieutenant Mark Rosen said the investigation is still open and couldn’t comment on the findings.
Friends and family have said that before her death she seemed to be committed to making a comeback with a new film.