(KRON/CNN) — Officials say a new wave of undocumented immigrants, mostly from Central America, are arriving on America’s doorstep.

The mayor of a border city in Texas says his conversations with recent arrivals reveal Trump’s campaign promises have a lot to do with it.

But as CNN found out, some immigrants say their arrival has nothing to do with the president-elect.

It’s a second south Texas border surge, and there are hardly any empty seats on the unmarked buses that pull into McAllen’s Central Station. Thousands of undocumented Central American families fleeing crime and poverty are again saturating America’s immigration system.

They turn themselves into authorities at the border, are processed, then released wearing an ankle monitor and the promise of returning for a court date.

Before heading north, Carlos Cardona, and his 4-year-old son, made a brief stop at a shelter that opened its doors during the immigration surge of 2014.

It’s run by sister Norma Pimentel.

“The violence, instead of diminishing, is escalating,” Pimentel said. “And so we have families that fear for their lives, especially of their kids.”

Volunteers have been walking these families from the bus station, to the shelter, and back for already two years now.

But what’s new are the numbers that we are seeing lately. Some of the officials in South Texas said they will also tell you there’s another reason why so many people are rushing to the US.

“They all know about President Trump,” McAllen Mayor Jim Darling said. “They all know about a wall. When you talk to them they know that.”

Mayor Darling suspects it’s no longer just violence and poverty in Central America, fueling this new wave.

“If you are talking about building a fence, and we are not going to let a lot of people in, you better get over here now before January and the swearing-in ceremony,” Darling said.

Among the crowds, CNN found 17-year-old Diriam Fuentes and her father Neri.

On the banks of the Rio Grande, more migrants emerge out of the darkness and turn themselves into authorities.

It’s a seemingly endless flow of families arriving night and day.

“There is a big fear in our community about what is going to happen,” Pimentel said. “Ultimately, we have to respond…to the fact that they’re human beings.”

Carlos Cardona and his son are starting the U.S. stretch of his journey.

Like so many others who are now in their shoes, they face an uncertain future.