LAPD has come out officially to dispute TMZ's story -- that the body of Celeste Rivas was partially frozen when it was examined -- but one source has doubled down.

A source connected to the L.A. County Medical Examiner insists Celeste's body was partially frozen when it was discovered inside a car registered to singer D4vd . This is in square contradiction to what LAPD is saying on the record.

It's interesting ... in one document from the Medical Examiner, it reads, "The decedent was not live scanned due to waterlogged fingers." Translation ... the M.E. was unable to fingerprint Celeste's body.

The Medical Examiner has put a security hold on the case ... as the LAPD continues to investigate. TMZ broke the story -- although the M.E. has not determined a cause of death, the LA

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