(CNN) Chain link fences, mattresses on the floor and families queuing to be processed -- and oftentimes separated. These are the photos of the processing detention center in McAllen, Texas, that the Customs and Border Protection agency wants you to see.

More than 1,100 immigrants -- including children -- were being held at McAllen when reporters were allowed in Sunday.

Dozens of protesters stood outside the center as reporters and democratic lawmakers arrived to learn more about the facility where the Department of Homeland Security is processing and detaining immigrants accused of illegally crossing the border.

The lawmakers came to south Texas, they say, to learn more about the agency's processing of undocumented immigrants entering the United States, including a Trump administration policy to refer all people who cross the border illegally for criminal prosecution on top of immigration proceedings.

As a result of enforcing that policy, families who cross illegally have been separated from their children because those accompanying the children are put into the criminal justice system.

Though media was able to tour the facility Sunday, they were barred from taking any pictures or video. CBP cited privacy concerns as the reason.

The agency released a handful of government images for publication -- showing McAllen through the lens of those controlling it.

Democratic Sen. Jeff Merkley of Oregon, who first visited the South Texas border on June 3, described his second visit as more coordinated for Customs and Border Protection officials who gave the tour.

"We did see the children who were held inside here," he told CNN's Ana Cabrera in an interview.

"In wire-mesh, chain linked cages that are about 30x30, a lot of young folks put into them. I must say though, far fewer than I was here two weeks ago.

"I was told that buses full (of children) were taken away before I arrived. That was one of my concerns, that essentially, when you have to give lengthy notice, you end up a little bit of a show rather than seeing what's really going on in these centers."

The warehouse-like facility has holding pens made from chain-link fences on the inside separating the immigrants.

Mattresses with thermal blankets were strewn on the floors.

Federal officials said the immigrants were only being processed and wouldn't be here longer than three days, but lawmakers reported they'd been told by immigrants within the facility that they had been there for seven.

Customs and Border Protection provided CNN with a document titled "Next Steps for Families" during the walk-through.

The document lists several steps for those in the government's custody and includes several actions for people to take under the question "how do I locate my children," including telephoning agency call centers and hotlines or emailing them.

CNN's Dianne Gallagher reported that families are brought through the warehouse and separated by the adults' gender, and that one woman approached CNN, crying and expressing fear about what would happen next.

The group of lawmakers included Sen. Chris Van Hollen of Maryland, Texas Reps. Filemon Vela, Vicente Gonzalez, and Sheila Jackson Lee, Vermont Rep. Peter Welch, Rhode Island Rep. David Cicilline, and Wisconsin Rep. Mark Pocan.

Speaking after visiting McAllen several Democrats expressed anger at the family separations and called on the Trump administration to change its policy.

"When you have a mother tell you directly that she's in fear that she will never see her child again, and when the United Nations Human Rights Commission indicate to the Trump administration that you are violating human rights, then you know that what we are saying today is President Trump, cease and desist," Jackson Lee said.



