PIJIJIAPAN, Mexico (AP) — On the 15th day of their journey, Joel Eduardo Espinar and his family were hurting. And they still had a country to traverse before they got to the United States.

A little more than two weeks before, they had fled Honduras and joined the migrant caravan of Central Americans snaking toward the border. Now, they assembled in the 3 a.m. darkness by a southern Mexico highway.

Jason, 11 years old, complained of stomach pains as he lay on the highway's shoulder. His 12-year-old sister Tifany Diana sat beside him, her head between her knees. The baby, Eduardo, was in his str...