Transcript for Trump: Migrant caravan traveling toward US 'national emergency'

And we begin tonight with the drama unfolding south of the border tonight. President trump watching very unclosely, and he's already made it very clear he will make this a major issue, just two weeks now until the crucial midterms. Thousands of migrants marching north through Mexico, hoping to reach the U.S. President trump calling it a, quote, national emergency, vowing to send in the U.S. Military. The president saying hiding in the thousands of marchers are violent criminals and people from the Middle East. Our team on the scene has found no evidence of that. Many of the families say they are trying to escape violence and extreme poverty at home. One woman overcome by the heat. There is no shelter, no food along the route. But the E the bait here at home tonight, should the U.S. Be their destination? ABC's Matt gtman along the route, where Mexican authorities have just responded tonight. What they're now saying about those migrants on the March. Reporter: The president is now calling it a national emergency. The caravan of migrants traveling towards the U.S. And you can see how many people are here, how many families just waiting for orders, waiting to see what they're going to do today. The caravan's numbers have grown since I began a week ago, 500 miles away in Honduras. About 7,000 people now traveling north. Their shortest route, 1,500 miles to Brownsville, Texas. President trump today tweeting, "Without any evidence, criminals and unknown middle easterners are mixed in." Take your camera, go into the middle and search. You're going to find ms-13, you're going to find Middle Eastern, you're going to find everything. And guess what? We're not allowing them in our country. Reporter: We took our cameras into the middle of the caravan and what we found were desperate families like Blanca and her three children. So, 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, so, it's just not safe, either in their home or their city. It's been three days since these people crossed into Mexico illegally. They were met with riot police and waves of tear gas. Some jumping off the bridge to the river below. Today, hungry and foot sore, they prepare to head out again. Ambulances sent by the Mexican government treating this baby. They marched on. So many clinging onto and off of trucks. This is incredible. They're riding atop this fuel tanker by the dozens, and they're being tossed foot and sandwiches and water. The heat suffocating. This woman collapsing before us. And Matt Gutman reporting in tonight from southern Mexico. And Matt, president trump has not made this a secret, he will push this hard, straight through the midterms. We've heard him bring it up at several rallies already. And there in Mexico, you've heard from authorities just moments ago holding a press conference, saying they're going to try to keep the migrants from getting any further north? Reporter: That's right. Over the past few days, we've seen them simply allow them right through and that's why you see these migrants pouring right past these ambulances and down this road. But now, they say, they're going to draw a line in the sand, not allowing them to go out of this state, and, of course, head northwards to the U.S. Border. David? All right, Matt Gutman in Mexico for us. Matt, thank you.

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