Homeland Security Secretary Jeh Johnson was unclear on Thursday about what happens to parents illegally in the U.S. when they try to claim their children who show up at the border alone, NBC News reported. While most children from Mexico are immediately returned, children from noncontiguous countries, like El Salvador and Honduras, are sent to shelters while U.S. officials attempt to find their relatives and decide whether they should be deported or allowed to stay. A sweeping anti-trafficking law and international agreements aimed at protecting children often guide U.S. policy on the issue. Critics have said the crisis has been caused by President Obama's push for immigration reform, particularly his decision to protect DREAMers — young illegal immigrants who have been in the U.S. for years — from deportation. Polls released this week suggest a majority of Americans support immigration reform.