Factual error: When the forensic crime scene investigator is asked how many bodies are in the house he states that they have not checked the attic or crawl space. The house is built on a slab foundation and would not have any crawl spaces. Easy mistake for a writer to make if they never lived in the southwest where such construction methods are employed. (00:05:30)
Suggested correction: Some houses in the southwestern US are built with crawl spaces, especially in areas on or near rugged terrain (as shown in the beginning of the movie). Also, it's possible the cartel dug in a crawl space to create extra room to hide more bodies.