No illegal drugs have been found in the hotel room where Whitney Houston died -- at least not yet -- but prescription drugs were present, and it's possible the singer drowned in the bathtub ... TMZ has learned.
Sources tell us ... when EMTs arrived Whitney's body was already removed from the bathtub so it will take an autopsy to determine if she OD'd, drowned or died from some other cause.
Informed sources tell us ... Beverly Hills cops -- who were still searching the room at the time this story was posted -- found various pill bottles. There was no evidence that Whitney was drinking alcohol in the room.
Whitney's body was just removed from the room on a gurney. It will go to the morgue for an autopsy to determine cause of death.