WHAT: Of the 2,500 Arizona border wildfires between 2006 and 2010, 422 were human-caused and burned more than an acre. At least 30 of these were linked to illegal border crossers by a new federal investigation.

HOW: Clues to wildfire causes included discarded bottles and food wrappers with Spanish-language labels near campfires adjacent to heavily used smuggling routes, according to the Government Accountability Office of Congress.

WHY: The GAO investigation was requested by four GOP senators led by John McCain, R-Ariz. “I hope this report is a lesson to … focus the discussion on the vital need to secure our southern border,” McCain said.