Whitney Houston died as a result of accidental drowning, in addition to the effects of heart disease and cocaine use, a coroner has ruled.

The soul superstar's body was found underwater in the bathtub of her Los Angeles hotel suite on 11 February, hours before she was scheduled to attend mentor and friend Clive Davis' annual pre-Grammys party.

A number of prescription pills were found in Houston's room but an autopsy conducted the day after her passing proved inconclusive.

Houston's cause of death was deferred pending toxicology results, and the Los Angeles County Assistant Chief Coroner Ed Winter subsequently requested all medical records from the singer's doctors to determine what drugs she was taking at the time of her death.

The findings of the autopsy report were released on Thursday and stated that Houston's death was accidental, although she also suffered from the "effects of atherosclerotic heart disease and cocaine use".

Traces of prescription drugs and marijuana were also found in her system, but are not thought to have contributed to her demise.

The report adds, "No trauma or foul play is suspected."

Houston, 48, had a long history of drug addiction and twice checked into rehab to control her substance abuse.

The L.A. County Coroner's full results are not expected to be released until a later date.