(TMZ) - Joan Rivers' autopsy has been done, but the Medical Examiner will need more information to determine exactly how she died ... TMZ has learned.

[Joan Rivers Dies At 81]

The Medical Examiner's Office tells TMZ they've completed the physical examination of Joan's body, but could not find a clear "cause and manner of death" ... pending further studies.

[Stars Remember Joan Rivers On Social Media]

TMZ reports those further studies will include conducting toxicology testing, and interviewing medical professionals who were present during the throat procedure Joan was getting last week when she stopped breathing.

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