The character of Kiki Camara, the police officer who takes the phone from Laura, is based on Enrique S. "Kiki" Camarena Salazar (1947 - 1985). Camarena was a Mexican-born American agent for the United States Drug Enforcement Administration who was abducted, tortured and murdered whilst on assignment (working undercover) in Mexico.
The character of Laura Guerrero was loosely based on Mexican model and beauty queen, Laura Zúñiga. On December 22, 2008, Laura Zúñiga along with seven men were arrested for narco-trafficking ties in Zapopan, Jalisco.
Mexico's official submission to the Best Foreign Language Film category of the 84th Academy Awards 2012.
The film poster is inspired by the album cover of Janet Jackson's 1993 self titled album, Janet, shot by Patrick DeMarchelier.