TUXTLA GUTIERREZ, Mexico — Police in Mexico's southern Chiapas state found 513 migrants on Tuesday inside two trailer trucks bound for the United States, and said they had been transported in dangerously crowded conditions.

Government of Chiapas via EPA

A handout photograph provided by the Government of Chiapas shows an X-ray view of the inside of a truck where some of a group of 513 illegal immigrants were found in Tuxtla Gutierrez, northern Mexico, on May 17. Authorities detected two trucks with immigrants from at least nine countries when the vehicles crossed a checkpoint equipped with an X-ray.

Chiapas state police discovered the migrants while using X-ray equipment on the trucks at a checkpoint on the outskirts of the city of Tuxtla Gutierrez.

PGJECH via EPA

A group of illegal immigrants are found inside a truck in Tuxtla Gutierrez, northern Mexico, on May 17.

Some of the immigrants were suffering from dehydration after traveling for hours clinging to cargo ropes strung inside the containers to keep them upright as the trucks bounced along from the Guatemalan border, and allow more migrants to be more crammed in on the floor. Read the full story.