Continuity mistake: After Melanie's "plan A" failed since the train is not at the station the group fights its way back to the prison. During that fight they kill quite a lot of the possessed miners. But in one of the following scene when those freaks assemble in the streets and walk to the prison there are only four or five bodies lying around.
Continuity mistake: Early in the movie, when Ice Cube is accidentally released by the two rookie cops, Natasha Henstridge offers herself as a hostage to obtain the release of the blonde rookie. Ice cube switches hostages and holds a knife to Natasha's throat. Right as she slips out of his hold, the knife pushes against her neck and for a split second you see the blade bend.
Continuity mistake: When everyone is exiting the back door of the prison, the police officers and Ice Cube are fighting creatures in the ally. After Ice Cube moves out of the way, the last male police officer is fighting, and when he headbutts one of the creatures he does not make contact.
Plot hole: When the Police first enter Shining Canyon, they make a point of mentioning why they don't have to wear a full breathing mask, because of the goggles they wear. (!) Later on however, several people who are not infected are not wearing the goggles, so they shouldn't be able to breathe.