Factual error: When Sheriff Emmett Kimsey (Lou Diamond Phillips) and Dr. Sheila Casper (Dina Meyer) enter the mine shaft and fall down into the cavern full of guano, they light a flare. The flame would have caused the fumes to ignite.
Revealing mistake: When they are about to start that freezing machine, the dead body where they took the key from still looks fresh as compared to the others they examined that are in an advanced state of decomposition.
Continuity mistake: Near the beginning of the film when the sherrif is smoking a cigar and talking on the bridge, the cigar changes position every time the camera cuts between a close-up of him and a wider shot.
Continuity mistake: Early in the movie when the Doctor is examining the teenager's dead body, his tie is first hanging down from his collar as he's bending over to look at it. Then the camera cuts in for a closer shot of him, his tie is now flipped over his shoulder.
Continuity mistake: In the scene when Sheila is looking at the pictures of the bat attacks, if you look at Jimmy, you can see him raising his arm and resting his head on his fingers, but after we get a close-up of the pictures, we go to a close-up of Jimmy and he's doing the exact same motion again.
