Send Help - What is that movie?

I have had a movie stuck in my mind of "need to re-watch" proportions. I don't know what year it was but I am sure that I watched it latest Spring 2009. It probably would have been in Spanish or English, though I watch other languages with subtitles.

The movie is about a group that lives together in an underground bunker and is filmed like Big Brother for a reality show. However, one of them flips his s**t and starts killing the others off.




What I know:

Released: (Latest) Spring 2009
Language: Most likely Spanish or English
Genre: Thriller, Horror, Psychological
Setting: Underground


ANY help will be awesome and appreciated because I want to re-watch this again! Thank you!!
~ Gracie