Whitney Houston reportedly had cocaine in her system before she accidentally drown

Whitney Houston had cocaine in her system when she died -- this according to the L.A. County Coroner.

The L.A. County Coroner has just released the singer's official cause of death -- accidental drowning ... but the report also notes heart disease and cocaine use were contributing factors to Whitney's demise.

Officials say Houston also had traces of marijuana in her system ... as well as Xanax (anxiety medication), Flexeril (muscle relaxer) and Benadryl (allergy medication).

A source connected to the investigation says: it is "very possible" Whitney had a heart attack that caused her to lose consciousness and drown. The heart attack may have been triggered by hardening of the arteries as a result of cocaine use.

Whitney was found dead in a bathtub at the Beverly Hilton hotel last month and several pills were found on the scene -- including Xanax, Ibuprofen, and Midol.

Investigators found NO EVIDENCE of cocaine in the hotel room.

Law enforcement sources says: from the beginning they did not suspect foul play -- and believe her death was not a homicide. Her family however had doubts about Whitney's demise -- suggesting there may have been foul play.