- Investigators found "a small spoon with a white crystal like substance " in her bathroom
- Coroner: Death was from accidental drowning; cocaine, heart disease were factors
- Her assistant left Houston alone for 35 minutes after telling her to take a bath
Los Angeles (CNN) -- Whitney Houston drowned face down in a tub of hot water about 12 inches deep, the final autopsy report on the singers death said.
The Los Angeles County coroner ruled that Houston's February 11 death was an accidental drowning with the "effects of atherosclerotic heart disease and cocaine use" as contributing factors.
Toxicology testing measured .58 micrograms of cocaine per milliliter of blood drawn from a vein in her right leg during the autopsy, the report said. The report did not explain the significance or effects of that level in a person's body.
Her cocaine use appeared to have occurred "in the time period just immediately prior to her collapse in the bathtub at the hotel," Chief Coroner Craig Harvey told reporters last month when he released the preliminary report.
Investigators found "a small spoon with a white crystal like substance in it and a rolled up piece of white paper" in the bathroom where Houston drowned, coroner's investigator Kristy McCracken wrote.
"Remnants of a white powdery substance" were found on a bathroom counter, McCracken wrote.
"I also collected remnants of a white powdery substance from out of a drawer and from the bottom of a mirror in the same drawer in the bathroom counter," she wrote.
Detectives found a "plethora of medications bottles" in the hotel room, although the coroner concluded the prescription drugs "did not contribute to the death."
Along with cocaine, the toxicology tests found other drugs in her body, including marijuana, the anti-anxiety drug Xanax, the muscle relaxant Flexeril and the allergy medicine Benadryl, the report said.
Houston was last seen alive by her personal assistant in her Beverly Hilton hotel room at about 3 p.m. that Saturday, the report said. The assistant left to run errands after telling Houston to take a bath in preparation for a pre-Grammy Awards party at the hotel that night, it said.
When the assistant returned to the locked room at 3:35 p.m.. she found Houston "lying face down in the bathtub filled with water, unresponsive."
"The assistant called for her bodyguard, and together they pulled the decedent out of the bathtub," the report said.
When paramedics arrived about 10 minutes later they moved Houston to the living room floor. It was at 3:55 p.m., 20 minutes after she was found by the assistant, that paramedics concluded she was dead, the report said.
A 60% narrowing of her arteries "suggest a cardiac event complicated by the cocaine use" led to Houston's slipping underwater, Harvey said.
"Something happened that caused her to go down and we know that when she slipped under the water she was still alive," he said. "We have evidence of drowning since there was water in the lungs."
Houston won six Grammys and sold 170 million albums, singles and videos over her career.
In recent years, the singer's accomplishments were overtaken by her struggles with drug addiction.
CNN's Jack Hannah and Kareen Wynter contributed to this report.
