Ciudad Hidalgo, Mexico — Mexican officials said they've begun their crackdown on Central Americans heading to the U.S. At the White House, President Trump waved a piece of paper that he claims is a secret agreement with Mexico to take even more aggressive steps to stop the flow.

Immigration agents in southern Mexico seemed eager to prove they're cracking down on Central American immigrants. It's a push to show the country will make good on a deal to avoid U.S. tariffs.

Mexico's foreign minister, Marcelo Ebrard, on Tuesday repeated his plan to send 6,000 members of a newly-formed National Guard to areas known to be migrant routes, an effort to stem the flow of asylum seekers to the U.S. Mexico, however, has in some ways already been doing that, deporting more Central American migrants in the last seven years than the U.S.

Many of them come through the Suchiate River which separates Mexico and Guatemala. Everyday along the river, people move goods to the other side to sell. But when migrants come over, they also hop on rafts. It's about $1 a person to ride.

The town's mayor, Sonia Hernandez, welcomes the National Guard and said she thinks it has diminished the number of people coming.

But just across the river in Guatemala, CBS News found Anselma and her four grandchildren looking for shelter. They said they're fleeing poverty and violence in Honduras and the U.S. is still their destination regardless of Mexico's plans.

While there is still no word on exactly when the Mexican National Guard will reach this river crossing, Mexico has 45 days to prove it can reduce the flow of migrants to the U.S. or be forced to negotiate again.