But, in its preliminary report, the coroner cites 'effects of atherosclerotic heart disease and cocaine use' as contributing factors in her death.
Coroner's spokesman Craig Harvey said drug tests indicated the singer was a chronic cocaine user.
Atherosclerosis is a condition marked by a fat buildup in the arteries.
Cocaine also constricts the arteries, and the combination of the two may have caused diminished blood flow to the brain and unconsciousness.
The 60% narrowing of her arteries "suggests 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."
There was no cocaine residue found in Houston's hotel room, which has prompted questions about whether someone cleaned up the scene before police arrived.
TMZ reports that a representative for Houston's boyfriend, Ray J, denies he had any knowledge that Houston was using cocaine.
At the time of Houston's death, investigators reportedly found prescription medications in her room.
Harvey said toxicology tests turned up marijuana, the anti-anxiety medication Xanax, the muscle relaxant Flexeril and the anti-histamine Benadryl in Houston's system.
But the coroner found that they did not contribute to her death.
"Those drugs were all at the therapeutic or sub-therapeutic level," Harvey explained. "They're not considered to be related to the actual cause of death."
Houston's sister-in-law, Patricia, released a statement saying, "We are saddened to learn of the toxicology results, although we are glad to now have closure."
The autopsy on Whitney Houston showed no trauma to her body and no sign of foul play.
While Beverly Hills detectives have met with the coroner and the case remains open, it will likely close when the coroner's office issues its final report.
Houston died February 11 in her room at the Beverly Hilton, the day before the Grammy Awards.
Police and fire officials were called to Houston's room after her unconscious body was found in the bathtub, just hours before she was to attend a pre-Grammy party at the hotel.
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.