Mexico is struggling to avert a collapse of law and order along its northern border in a region that generates a quarter of its economic output, with two states already facing the threat of criminal anarchy. Even after four years of dramatic military sweeps, drug trafficking organizations in Chihuahua and Tamaulipas are extending their control over large areas and the state governments seem powerless to stop them. Mass jail breaks, abandoned police stations, relentless killings and gangs openly running criminal rackets such as gasoline stolen from pipelines are the new reality in regions once at the forefront of Mexico's efforts to modernize and prosper under the North American Free Trade Agreement.