PAMPLONA, Colombia — The walking began before dawn: Before the clouds broke against the mountaintops, before the trucks took over the highway, even before anyone in the town woke up to check the vacant lot where scores of Venezuelan refugees had been huddling through the night.

Children, grandmothers, teachers, nurses, oil workers and the jobless had all sprawled there together — bound by a collective will to put as many miles as possible between themselves and the collapsing country they had fled.

All but Yoxalida Pimentel. She could not take another step.

“After so many hours of walking, after days, nights, sun, cold, rain — I lost my baby,” she said, crying alone the morning after her miscarriage.

The economic crisis that has engulfed Venezuela under President Nicolás Maduro has set off a staggering exodus. The economic damage is among the worst in Latin American history, researchers say, with more than three million people leaving the country in recent years — largely on foot.