In the US, the Trump administration faces serious criticism for its policies on undocumented Mexican immigrants. Hundreds of children who crossed the border into the US have been taken away from their parents, and kept in cages in tent cities along the border. CNN's Dianne Gallagher was given exclusive access to one processing center in the US state of Texas, and shared this report with CGTN.

DIANNE GALLAGHER MCALLEN, TEXAS "I'm in McAllen Texas. Behind me there you see the Rio Grande Valley centralized processing center. They have a greater intake when it comes to processing undocumented people coming into the United States than any other in Texas.

Now I went inside and I took a tour myself and, we should go ahead and say this is a tour that was guided by border patrol agents. So, we saw what they wanted us to see in this case. But we did get a chance to talk to people who were being held in, what I can only describe as cages. We're talking about twelve-foot chain link fences here, some of them housing single adult males, others housing single adult females, and then you go into a warehouse room where you see families that are together.

Younger children are with either a father in one sort of pen area, or a mother in another sort of pen area. There you see also we had a pit inside where there were so many young boys. Now some of them are undocumented minors, we're told, others were teenagers they were keeping out of those family units.

But at this facility they're only here for, they're supposed to be a maximum of 72 hours, some of the people I spoke with told me they've been here four or five days. But this is a temporary facility. They move on to either federal court if you're an adult or under the zero-tolerance policy, the children move on to a government holding area, or group home, or some other facility to hold them until they can either be reunited back with their parents or figure out what the next step is.

Now when I spoke to a few people in here one woman, a 24-year-old from Guatemala, she had her 1-year old daughter with her. She'd been separated from the group that she came across the border with. She said that she was unaware of the zero-tolerance policy. There was some high emotion in there, a lot of the children those unaccompanied minors that I spoke to, they told me they were there by themselves. They were happy just to be out of the elements, one boy said.

But they're just kind of sitting there being good and it is a little sad to see young children 3, 4, 5 years old with their father a mother just sitting on a concrete floor, or a metal bench, where they have these mattresses that are piled up in these 12-foot chain link pens.

So, the senators came down here as well touring. They're touring another facility in another part of Texas. They're trying to bring attention and awareness to see if they can put political pressure on the president to put an end to this policy. Or just to essentially say, stop doing it because it's not a written law at this point."