MEXICO CITY (AP) — A truck loaded with Central American migrants crashed in southern Mexico on Tuesday, killing one and injuring dozens more, authorities said.

Images posted online by Mexican media outlets showed the crumpled truck on the side of the road and health workers treating the injured at the scene. Some were bleeding from the head, and there was at least one child in the group.

The Civil Defense department in the Gulf Coast state of Veracruz gave the injury toll as 81.

Mexico’s National Guard said the crash was reported at 8 a.m. and those on board were undocumented people mostly from Guatemala but also Honduras and El Salvador.

Those three countries make up the Northern Triangle region of Central America, a source of significant outward migration by people fleeing violence and poverty.

The Guard said that the driver of the vehicle had not been located.

Seventy-six people were taken to hospitals in the cities of San Andres Tuxtla and Santiago Tuxtla, both of which lie on the highway where the accident took place. A temporary shelter was set up in San Andres Tuxtla for those with minor injuries not requiring hospitalization.

Mexico has moved more aggressively to stem the irregular flow of migrants and asylum seekers through its territory bound for the United States, especially following the threat of U.S. trade sanctions last year.

It says its priority is combating people-smuggling operations, which often lead to people from Central America and elsewhere being crammed into overcrowded vehicles. Such conditions can be dangerous, as when migrants are locked in overheated tractor-trailers.

The government has also cracked down on the large caravans of migrants and asylum seekers traveling together by foot. On Jan. 23, some 800 people mostly from Honduras were forced onto buses in the southern state of Chiapas as authorities broke up what remained of the most recent caravan.