From foxnews.com:
In a second, equally explosive disclosure, a law enforcement source tells Fox News, that ATF undercover agents were acting as the straw buyers and purchasing guns using government-issued false identifications and then providing those guns to cartel traffickers to gain credibility in their undercover roles. In that capacity, the ATF “provided 2, 50 cal. machine guns to traffickers that are loose in Mexico and unaccounted for,” the source said.