Mexican drug cartels pay Americans to smuggle weapons across the border, intelligence documents show

Mexican drug cartels have been smuggling a vast arsenal of even military-grade weapons out of the U.S. with the help of American citizens, a CBS Reports investigation has found.

Exclusively-obtained U.S. intelligence documents and interviews with half a dozen current and former officials reveal that the American government has known this for years but, sources said, it's done little to stop these weapons trafficking networks inside the United States, which move up to a million firearms across the border annually, including belt-fed miniguns and grenade launchers.

Dozens of cartel gunrunning networks, operating...