The studio did not cast any character as a lead. Director Renny Harlin wanted no dummy characters or obvious victims and established a sense that "anyone could die at any moment" in the film.
The primary reason the film was able to be done on such a modest budget was due to a generous tax break from the Dutch government.
(at around 31 mins) The dominoes used in the domino close-ups were actually ten times the size of normal dominoes.
Clifton Collins Jr. prepared for his role by regularly traveling historic Hollywood Boulevard in a wheelchair and worked with a doctor to ensure an accurate depiction of a person with a disability.
As part of LL Cool J's preparation, he lost nearly 40 pounds and spent time with homicide detectives in the Philadelphia (PA) Police Dept.
Renny Harlin: [Finland] (at around 45 mins) When the others leave Vince and Gabe alone in the basement room, Finland's flag is seen on the wall.
Renny Harlin: [Finland] (at around 4 mins) In the beginning of the movie, when Reston and Morris are about to enter the house, there is a small hockey player figurine with a Finnish flag in the car that Reston plays with.