The kidnapping of four US citizens in northeastern Mexico, two of whom were found dead, was likely the result of a mistake by alleged drug traffickers who mistook them for other people, Mexican authorities say. "The line [of investigation] that it was a mix-up, and not a direct aggression, is finding more and more ground," Irving Barrios, prosecutor for the northeastern state of Tamaulipas, says at a press conference in Mexico City. IMAGES AND SOUNDBITES