MCALLEN, Texas - Customs and Border Protection employees call them "family units."
It's here that migrant families are kept when they are nabbed trying to enter the United States illegally - one in a series of 30-by-30-foot fenced-in "pods,' or cages, each able to hold 20 to 30 people.
This is home while they wait to learn the next phase in their immigration journey.
There is not much room for children to play. But two young boys, on Sunday, manage.
They tested each other's strength by pushing and pulling one another while their arms were intertwined.
They jostled around while being careful not to step on the Army green bed-shaped cushions that lined the floors or slip on the foil-like Mylar space blankets they use at night. Agents say they're a more sanitary option for the thousands who pass through the Ursula Border Patrol Processing Center in McAllen.
The roughly 77,000 square-foot warehouse-like facility is the first stop for those detained by agents in the Rio Grande Valley Sector. On Sunday, 528 families and 197 unaccompanied minors were being housed there.
For some, it's the last place they will be together as a family. The adults brought here are criminally prosecuted for illegal entry as part of a new deterrence effort referred to as the "zero tolerance' policy.
.@JulianCastro and Leah, whose parents are undocumented, attempted to deliver letters of love and stuffed animals to families in detention at the @CBPSouthTexas processing center in McAllen, where the #FamiliesBelongTogether campaign gathered for a #FathersDay rally today. pic.twitter.com/ZLnCrMQlc4- Beatriz Alvarado (@CallerBetty) June 17, 2018
In the past, illegal entry has been handled as a civil matter.
"(Past presidents) decided there was one place they would never go and that was to separate families,' said Rep. Filemon Vela, D-Texas. "This administration … has made that decision.'
On Sunday, Father's Day, U.S. Sen. Jeff Merkley, of Oregon, led a group of Senate and House members on a tour of the U.S.-Mexico border to "further investigate' the policy that is separating migrant families. The processing center in McAllen was one of several stops.
Other lawmakers included Rep. Peter Welch of Vermont; Rep. David Cicilline of Rhode Island; Rep. Mark Pocan of Wisconsin; Sen. Chris Van Hollen of Maryland, and Texas Reps. Vicente Gonzalez and Vela.
The trip follows Merkley's attempt earlier this month to investigate the family separation policy. On that trip, he was barred from entering a children's detention facility in Brownsville.
The processing center in McAllen has resorted to virtual processing due to the influx of detainees since the policy was announced, said John Lopez, acting deputy patrol agent in charge.
Inside, Van Hollen said the delegation met a woman from Guatemala who came seeking asylum and had been separated from her teenage daughter.
"This is a deliberate and inhumane policy, and we're here to say to President Trump to end it today,' Van Hollen said.
At least 2,000 migrant children have been separated from their parents since April, when the Trump administration announced its "zero tolerance" immigration policy.
The practice of separating children from their parents has been touted by the administration as an amplified effort to deter migrants from entering the U.S. illegally. It also has gained global attention, including a plea from the United Nations High Commissioner for Human Rights to "immediately halt" the practice.
A criminal background check determines if a child under 5 years old will be separated from his or her parents, said Carmen Qualia, the assistant chief patrol agent.
Rio Grande Valley Border patrol sector Chief Manuel Padilla directly attributed the lack of the "zero tolerance' policy to an uptick in families and unaccompanied minors entering the country illegally beginning in 2013.
"Because we did not enforce the law - there (were) no consequences for family units and unaccompanied children - we saw that spike in June 2014.
"That created the crisis of 2014.'
The group of lawmakers also toured Casa Padre, a shelter for unaccompanied minors operated by Southwest Key Programs in Brownsville, the facility that denied Merkley entry earlier this month.
"The vast majority of the children arrived at the border unaccompanied," Merkley said Sunday. "But a certain share of them came with their parents and they were separated from their parents."
Other sites the delegation visited included one of the bridges where the administration is reportedly slow-walking entry for asylum seekers who are trying to legally enter the U.S.
"The bottom line is this is being used by the president as a tactic, a negotiating tactic," Welch said. "It's truly astonishing that the president is going to hold hostage these kids to get his way on a (border) wall.'
Families, advocates and allies rallied in front of the processing center in McAllen in support of the children held inside without their parents on Father's Day.
The crowd chanted "you are not alone" and "families belong together."
On the East Coast, Democratic members of Congress from New Jersey and New York on Sunday met with immigration detainees separated from children at the southwest border who are now being held at a New Jersey immigration facility.
House Speaker Paul Ryan plans to bring up two competing Republican immigration bills this week - and neither seems likely to pass.
The first GOP bill is a hardline measure that would cut legal immigration, strengthen border security, and provide temporary legal status to the so-called DREAMers, undocumented immigrants brought to the U.S. as children. President Trump and conservative lawmakers back that proposal, but moderates do not. And it doesn't have enough votes to pass the House.
The second bill is a "compromise" being crafted by GOP leaders and aimed at bridging the divide between the moderates and the conservatives. That bill is still under wraps, but conservatives are wary that it will go too far in granting what they see as "amnesty" to the DREAMers.
"Neither bill is going to pass next week," Mark Krikorian predicted last week. Krikorian, executive director of the Center for Immigration Studies, which supports strict limits on immigration, said, "There clearly isn't a consensus ... and they'll just move on to the farm bill or whatever the next thing is."
Contributing: Eliza Collins, USA TODAY. Follow Beatriz Alvarado on Twitter: @CallerBetty
Here's the "zero tolerance" policy:
California officials quickly determined an arsonist started last month's huge wildfire southeast of Los Angeles, and that two weeks earlier sparks from a vehicle produced a deadly wildfire in the far northern part of the state.
A downtown San Diego high-rise condo complex was evacuated early Sunday morning due to a water pipe bursting.
The showdown begins Monday between the Trump administration and a handful of states opposed to relaxing fuel economy standards .
A 37-year-old man riding a bicycle was hit by a vehicle, seriously injured, and the driver sped off, officials said Sunday.
An armed man robbed an eatery in Rancho Bernardo, pistol whipped an employee there, but was unable to keep the money he had taken when he ran into a pillar during his escape, dropping the money but not his gun, a police officer said Sunday.
A 64-year-old man collapsed and died on a hiking trail in the Cleveland National Forest near Alpine, the county Sheriff's Department said Sunday.
Cooler Sunday into Monday as a trough transits across the West Coast. Temperatures warm again through mid-week.
San Diegans and tourists alike headed to the coast to take in all that the first day of fall has to offer.