In an interview with TerrorTrap.com director George Mihalka said that the shooting location at Sydney Mines, Nova Scotia was chosen because of its rustic atmospheric appearance, but when the locals found out that a movie was to be shot there they decided to spend tens of thousands of dollars to have the mine painted and cleaned. This, of course, diminished the reason that the production wanted the location to begin with. Mihalka said that $75,000 of the film's budget was then used to return the mine to its original state for shooting.
The film was shot in authentic mines which were often as much as 900 feet underground. Only certain lighting devices could be used in the mines because of the potential danger of methane explosions.
The filming location, Sydney Mines, Nova Scotia is a small Canadian coal-mining town. The area was filled with closed pit mines, bootleg mines and underground mines, which were shutting down (due to economic and environmental issues), at the time filming took place. Since then, the mine used as the "Hanniger Mine", called the Princess Colliery Mine in real-life, has been dismantled, buried and turned into a park/museum.
According to makeup effects artist Thomas R. Burman, one of his gory creations was realistic enough that director George Mihalka threw up at the sight of it.
The folk ballad that plays over the ending credits was added by composer Paul Zaza as an afterthought. The uncredited singer who does the vocal for the ballad was Scottish-Canadian tenor John McDermott.