MEXICO CITY, June 28 (Reuters) - Mexican authorities on Monday found a boy thought to be about 2 years old alone near an overcrowded truck that had carried more than 100 migrants in suffocating conditions, the national immigration institute said. Wearing no shirt, the boy stood by himself, surrounded by a handful of packaged snacks, half-empty water bottles, clothes from other migrants and black trash bags scattered on the ground, a partially blurred photograph released in a statement from the institute showed. In the picture, the boy appeared to be holding his face in his hands. Another image apparently taken later showed him dressed and in the care of state authorities. Most of the travelers fled before authorities arrived at the scene, but eight Central American adults who remained behind described the situation and said the migrants had demanded the driver stop after several fainted from dehydration and lack of air, the institute said in a statement. "None of the adults said that they were a family member of the minor," the statement said, adding that authorities were in contact with the Guatemalan consulate because the boy could be from that country. Thousands of children from Central America have crossed illegally from Mexico into the United States without their parents this year, according to U.S. Customs and Border Protection (CBP) data. Last week, U.S. Vice President Kamala Harris visited a border patrol facility near the U.S.-Mexico border and urged a focus on children and practical solutions to migration.