UN Official: “Extensive use of immigration detention leads to tragedies like this one.” The fire-related deaths of at least 39 migrants in a detention facility in Ciudad Juarez, just across the U.S. border with Mexico, will likely be found to have had several contributing factors. There was the immediate cause of the blaze, the mattresses apparently set alight by desperate men in the center to protest their imminent deportation. And then there is the apparent role of guards, seen on video walking away from the blaze. But as an expert on immigration policy, I believe there is another part of…