The film was shot in the fall of 2007, nearly four years before it was finally released.
Director Stevan Mena's initial cut of the film was three hours long. Post production work on film in order to cut it down to its final length involved some re-shoots and cutting back the gore scenes in the film. Mena said in interview for Fangoria, "The original cut was extraordinarily bloody, and we just felt there was no way we were going to get it to any kind of a wide audience with that amount in it. So we toned it down a bit-not to the detriment of gore fans, it's still a very violent movie, it's just a little more watchable now. There were also certain story elements that I felt needed a bit more attention, and I had the opportunity to go out and make it better, which I did." Director's cut of the film was released in October of 2018.
The old building used as a location for the abandoned slaughterhouse was indeed an abandoned slaughterhouse.
The scenes at the Drive-In movie theater were filmed at Shankweiler's Drive-In, the oldest operating Drive-In in America located in Whitehall PA. It was the second Drive-In ever built in the United States.