Plot hole: In the scene where they go to the intern's apartment to find the key to go out the through the basement there is a moment where they can't remember which apartment belongs to the intern. When they ask the cop who did roll call he can't remember. Angela says that in order to figure it out they should go check the mailboxes in the lobby and match up the name. This would lead them back past all the infected people and undoubtedly make the movie more interesting but it would have been safer and quicker to rewind the tape in the video camera and see which apartment the intern claimed when his name was called.
Suggested correction: It definitely would not have been the safer option. Where would Pablo, Angela and Manu have stood while rewinding and starting the tape to get to the required footage? The apartments that are open all contain infectees (Ms Izquierdo, Jennifer, the young cop, Cesar, health Inspector), and the other infectees are roaming the hallways and staircases looking for survivors. It would have been far more dangerous to stand still out while rewinding footage, than to check the mailboxes.
