TORNILLO, Texas -- A newly-opened "tent city" along the Texas border is now at the center of the national immigration debate. The camp is housing teenage boys who illegally entered the United States -- unaccompanied by an adult.

They're being moved there to make room at shelters for a growing number of migrant children who were separated from their parents under the Trump administration's "zero tolerance" immigration policy.

Thousands of protesters chanted and held signs Sunday, demanding the Trump administration stops separating children from their parents at the border.

Thousands came out to protest Trump Administration's policy of separating families. #Tornillo is where the first tent city has been set up, with the possibility of holding 4000 children. More on the #immigration debate on @CBSNews w/@Elaine_Quijano tonight. pic.twitter.com/FqvQZLc84a — Mireya CBS (@cbsmireya) June 17, 2018

The march was organized by Democratic Congressman Beto O'Rourke.

"We were told there were 98 kids in this tent city yesterday, we were told today there are 200 kids," O'Rourke said. "We've all got to own this, we cannot blame this on Trump, we cannot blame this on a political party -- this is America right now, and so America's gotta show up."

This federal detention facility in rural El Paso is being used to house "unaccompanied minors."

The teen boys began arriving Friday.

"My husband just said 'it's been a long time since I was in a protest march -- back when we were protesting against Vietnam,'" Jane Boyd told CBS News.

"It's facilities that you would see if you went to any kind of natural disaster site, tents like the U.N. uses," said Rep. Will Hurd, R-Texas.

Hurd has been inside the encampment, currently housing 16 and 17 year-old boys.

"There are 20 kids per tent, there's two adults in the room," he added.

Hurd's district stretches across the Texas-Mexico border.

"My constituents that are outraged ... they should know that I'm outraged too," Hurd said. "What's happening in Tornillo is a symptom of a larger problem."

For now, the tents are considered overflow and occupants are being moved to them from other shelters.

The Department of Homeland Security numbers show that over a six-week period, nearly 2,000 children were separated from nearly as many adults.

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Jaclyn Allotta brought her two children to protest Sunday.

"I'm here because I grew up in a border town and now live in a border town, this just pulls at my heart strings," Allotta said. "For me it's not a political issue, it's a mother issue, it's a neighbor issue, it's a what's right issue."

Despite a number of requests, CBS News is not being allowed inside -- not even near the perimeter of the facility. Officials said there are 200 kids inside now, but at capacity it can hold up to 4,000 children.