There is a whole industry in Central America wherein men are hired drive a truck filled with stuff from the United States down to countries south of Mexico. The cargo may be legal merchandise, stolen goods, or a mix of both. Washington D.C. could easily be part of the transmigrante network.
Read a description of the scheme, excerpted from a long, harrowing story of one Colorado Guatemalan family's involvement:
Drive along the highways of south Texas, or in Mexico’s eastern states of Tamaulipas, Veracruz, and Tabasco, and they’re hard to miss: caravans of used passenger vehicles, usually old pickup trucks, heading southbound toward Central America. Oftentimes, the used autos are piled high with secondhand goods, such as washing machines and motorbikes, and they’re typically hauling a second passenger vehicle behind them with torn pieces of duct tape spelling out “In Tow” on a rear hitch or window. The drivers of these vehicles are transmigrantes, a term derived from a special visa program that the Mexican government devised to allow goods and vehicles to move overland from the United States to Central America along designated highways and without drivers having to pay high import-export fees.
According to the U.S. Department of Homeland Security, the idea behind the program was to allow families in the United States to move—or transmigrate—across Mexico to Central America while not imposing heavy customs duties on items they brought along with them. Other times, individuals from the United States use the visa to personally transport goods (which they’re not allowed to sell in Mexico) to family members in Guatemala, Honduras, and El Salvador, often during the holiday season. Over the past three decades, though, an entire industry of freelance truckers has arisen around the program and its tax loopholes.