BROWNSVILLE, Texas — The Trump administration has selected Tornillo, Texas, for the construction of tents to house the overflow of immigrant children, many of whom have been separated from their parents under a new "zero tolerance" policy, according to three sources familiar with the decision.

The Department of Health and Human Services will erect a "tent city," full of large tents whose walls touch the ground, that is estimated to hold 450 beds for children, say the sources.

It will not be the first time the U.S. government has erected tent cities to house immigrants. U.S. Customs and Border Protection used tents to house an influx of immigrants in 2014 and at the end of the Obama administration. But now the overflow of a particular immigrant population — in this case, children — is a government-created problem.

The access to the Tornillo-Guadalupe international bridge in Guadalupe, Mexico. Tomas Bravo / Reuters file

The increase of children who are alone and in need of care at the border is the product of a new Trump administration policy that on May 7 began criminally prosecuting all adult migrants crossing the U.S.-Mexico border between ports of entry. As a result, the Department of Homeland Security separates any children traveling with those adults before prosecution.

One shelter in Brownsville, holding nearly 1,500 boys aged 10 to 17, opened its doors to reporters on Wednesday. NBC News was among the first to tour the facility, which closely resembled a jail and allows children outside for only two hours per day.

The overflow of children at HHS facilities has caused backup at border stations, the first stop for immigrants crossing into the United States. As of last week, over 570 unaccompanied children were in the custody of the U.S. Border Patrol, and nearly 300 of those had been held for more than 72 hours, the limit for holding an immigrant of any age at a border station.

Ron Vitiello, acting deputy commissioner of Customs and Border Protection, told MSNBC on Thursday that about 1,500 immigrants are being arrested each day for crossing the border illegally. Vitiello said the policy is meant to deter families of immigrants from coming to the U.S.

"If you apply consequence to illegal activity you get less of it," he said in defense of the policy. "They are only in these shelters long enough to be reunited with their family members. That's the purpose of them."

The facility in Brownsville is holding children for 52 days on average. They are sometimes sent to foster homes if relatives in the U.S. cannot be found.

Just confirmed with @ckubeNBC: @HHSGov has selected Tornillo Land Port of Entry near El Paso as the first temporary shelter location.



It will have 450 beds.



Kids will sleep in tents. — Jacob Soboroff (@jacobsoboroff) June 14, 2018

"HHS is legally required to provide care and shelter for all unaccompanied alien children referred by [the Department of Homeland Security], and works in close coordination with DHS on the security and safety of the children and community," a spokesman for HHS said in a statement.

Jacob Soboroff reported from Texas. Courtney Kube and Julia Ainsley reported from Washington.