Transcript for Thousands endure brutal conditions in migrant caravan bound for US border

Reporter: Tonight the Mexican government saying it won't allow this caravan of thousands of foot sourced Central Americans March further towards the U.S. And president trump calling it a national emergency. Take your cameras, and go into the middle and search. You're going to find ms-13 and Middle Eastern, you're going to find everything, and guess what, we're not allowing them in our country. Reporter: So we took our cameras again today into that my grant caravan and what we found were desperate families. The caravan's ranks have swollen since it began 500 miles away and a week ago in Honduras. About 7,000 people now traveling north, the shortest route to the U.S., the 1,500 miles to Brownsville, Texas. They crossed into Mexico illegally on Friday, some of the migrants tearing through a border gate. They were met with riot police and waves of tear gas. Some jumping off the bridge to the river below. Yesterday they walked 25 miles to the next town of tapachula and this morning they treated their battered feet and bodies, this baby being treated for heat exhaustion with a syringe full of medicine. Five miles into their March they approach the village of viva Mexico with good samaritans. More manned more hitching rides. Mexican authorities allowing them through. What slowed them was the heat this. Woman brought into town in a van, unconscious, and they lay her down but more were coming. Medics came and tended to them. Blanca has been marching for days with her three children. For Blanca there is a serious concern that the gangs who killed her husband are going to come back for her family and the rest of them, but nothing is worse, she said, than turning back.

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