Dec. 20 (UPI) -- This past weekend, during a routine inspection at an Interstate 25 checkpoint in New Mexico, U.S. Border Patrol agents discovered and apprehended 37 undocumented migrants trying to hide inside a tractor trailer, officials said. The agents, assigned to the Las Cruces Station in the El Paso sector, heard movement near the rear door of the trailer and, according to U.S. Customs and Border Protection officials, "observed individuals attempting to crouch behind freight."