The camera used during the car-attack scene got so much fake blood on it during shooting that when it was being used on another film later on fake blood oozed from it during the focusing of a shot.
According to Alexandre Aja the scene where Marie hides from the killer in the gas station restroom is a homage to a similar scene in Maniac (1980).
The film is set in the south of France, but it was shot entirely in Romania, due to budgetary reasons and the availability of similar locations.
The location used for the exteriors of Alexia's house was actually a dilapidated mill that the production cleaned up and dressed for the film.