Nancy Grace Says Gabby Petito Cause of Death Might Be Hidden by Elements, Animals

Nancy Grace says determining Gabby Petito's cause of death could be hampered by the wildlife of Wyoming -- but, adds, the fact her tattoos were ID'd offers a glimmer of hope.

The author and Fox Nation host joined "TMZ Live" Tuesday and said she's not sure Tuesday's autopsy will ultimately determine how Petito died ... or if her fiance, Brian Laundrie, was involved.

Her theory? The site where authorities found remains matching Gabby's description experiences such intense weather elements, it could have caused decay or damage to the body that might conceal markers the coroner would use to determine cause of death.

Nancy -- who's special, "A Gabby Petito Investigation" is streaming now on Fox Nation -- points out there's also a lot of wild animal activity in that area, and it's possible the creatures could have damaged the corpse.

That being said, Nancy says there's hope Gabby's body was found somewhat, if not fully, intact. Remember, the FBI said the body they found was "consistent with the description" of Petito.

Nancy says, that if authorities were able to immediately identify Gabby's tattoos -- on her left arm and right forearm -- it's possible her skin was still intact ... meaning the body could offer clues about what led to her death.

With all we know at this point, she sees 3 possible explanations for Gabby's disappearance and possible death. She also tells us why she thinks cops never named Laundrie a suspect.

As for Laundrie ... he's been missing for days now but a trail cam set up in the wilderness in Baker, FL may have spotted him. The FBI is investigating the possible sighting.