Their names are a mystery and in some cases, their faces are too.
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But the stories of the children caught in the crosshairs of the "zero tolerance" policy at the border are resonating with people across the country.
Here are some of the stories of children whose experiences have captured the nation's attention.
The girl pictured crying for her mother
One of the most iconic images of the border crisis featured a 2-year-old girl from Honduras.
John Moore, a special correspondent and senior staff photographer for Getty Images, took the photo after spotting the girl in her mother's arms while he was participating in a ride-along with Customs and Border Protection agents in Texas.
He saw a group of roughly 20 mothers and children late on June 12, "gathered on a dirt road" in a part of the Rio Grande Valley and, upon approaching the group, he saw the girl in her mother's arms.
Moore said that he saw that the mother was breastfeeding her daughter "to keep her calm" and that, later, one of the agents asked the mother to put her daughter down.
"Once the mother put her on the ground she started screaming immediately," Moore said.
The mother and daughter were taken away from the scene together, and because their names are unknown, it remains unclear if they were separated, though the policy mandates that if the mother faced charges they would be separated.
Read more about Moore's experience here.
The boy put in foster care with American parents
When a 9-year-old Guatemalan boy arrived at a Michigan foster care home, he was so afraid he couldn't eat.
Over time, the boy, whose name has not been released, confided to his foster parents that he and his father had escaped violence and poverty in their homeland only to be greeted with more hardship when they arrived at the U.S.-Mexico border, where the boy watched his dad being taken from him in handcuffs.
"When he came to us, he was extraordinarily fearful,"said Jen, the new foster mother of the boy, who asked ABC News not to use her last name to protect the family's privacy. "He came in all-black clothes, we learned, because he traveled at night with his dad and they didn't want to be seen."
The child handed them a piece of paper from a packet his mother had sewn into his pants before he and his father left home. The paper contained phone numbers of people his family knew in the United States, as well his mother's phone number in Guatemala.
While a Michigan caseworker was collecting the father and son's intake information, she called the mom's phone and she answered.
"He was overcome," said Jen. "He couldn't talk. He was crying so hard he was almost to the point of being sick."
Over the past eight months, the boy, now 10, opened up - telling caseworkers the story of his and his father's treacherous journey to what they thought would be the land of promise.
Read more about the boy's journey here.
The heartbreaking audio
The recording first reported and released by ProPublica of crying children in one of the shelters included the voices of a number of distraught children, and one of them has since been identified.
Alison Jimena Valencia Madrid is a 6-year-old girl who fled gang violence in El Salvador with her mother.
She's heard on the tape asking an official in Spanish, "Are you going to call my aunt so that when I'm done eating, she can pick me up?"
She memorized her aunt's phone number, and the aunt told ProPublica that she was allowed to make the phone call, but it was still heartbreaking.
"She’s crying and begging me to go get her. She says, ‘I promise I’ll behave, but please get me out of here. I’m all alone,'" the aunt told ProPublica.
Watch our video report about her story here.