Republicans are stepping up their scrutiny of dozens of shelters run by aid groups on the U.S. border with Mexico. President-elect Donald Trump’s allies consider the shelters a magnet for illegal immigration. Many of them are nonprofits that rely on federal funding. Trump’s incoming border czar has vowed to review the role of nongovernmental organizations and whether they helped open the doors to the immigration crisis. The developments have alarmed immigration advocates and some officials in border communities, including Republicans. They say communities can collapse without shelter space or a budget to pay for humanitarian costs. Aid groups say they are responding to emergencies foisted on border towns.