The Mexican cartels use the cleared pathways over the oil pipelines from Mexico into Texas as smuggling routes, and "these unpatroled, unmonitored corridors make ideal execution sites for errant couriers, business rivals, informers, and unwitting migrants who stray into the wrong place at the wrong time" as reported by Joe Carroll for BloombergBusinessweek:
For Michael Vickers, a 64-year-old veterinarian, the wave of violence has been overwhelming. In the past two years, 216 corpses have been found near the pipeline pathways within 15 minutes of his doorstep. It’s certain that many more haven’t been found: The wild, unforgiving terrain and fauna hide much evidence. "The wild hogs gobble up a lot," he says.
And the Obama adminstration insists there is no evidence of spillover violence in the United States from the Mexican cartels.