YUMA, Ariz. (NewsNation Now) — Since November alone, Yuma County, Arizona has recorded more than 36,000 unaccompanied minors crossing the border from Mexico into the U.S, according to County Supervisor Johnathan Lines, who called the situation “tragic.”

“I’ve had kids as young as 5 years old come across by themselves right here,” Lines said, motioning to an incomplete portion of the border wall in Yuma.

According to the Council on Foreign Relations, a non-profit think tank based in the U.S., the immigration authorities encountered nearly 150,000 unaccompanied minors at or near the U.S.-Mexico border during the last fiscal year.

That number is an all-time high, even though it temporarily slowed down in October.

The term “unaccompanied minor” doesn’t always mean that a child traveled to the country by themselves. Some are separated from family at the border or left behind by smugglers, according to the council.

Guatemala, Honduras and Salvador are some of the top countries of origin among unaccompanied migrant children. Their travels are fueled by struggles with poverty, crime, and natural disasters, the U.S. Department of Health and Human Services has said.

Throughout the day Tuesday, NewsNation reporters witnessed groups, large and small, cross the border into Yuma. Many had small children. Other groups consisted only of children.

The wall throughout the Yuma sector was meant to act as a barrier between U.S. and Mexico. Instead, more than 1,000 people — often children — cross the border into Yuma each day, Lines said.

On Tuesday, one teenage girl from Peru crossed into the U.S. through the Yuma Gap in Arizona after sundown. She sobbed and held a toddler in her arms as two other young children walked beside her, out of breath.   

Two months earlier, border patrol officers came across a 2-year-old boy navigating the cold basin water on his own.

“He was wandering in the bottom of this basin with a note that said ‘My mom lives in South Carolina’ written in Spanish,” Lines said. “His father had just told him to cross — a 2-year-old.  He was completely soaked. Some ladies from Honduras found him and brought him up to the agents.”

Unaccompanied children who are apprehended by Homeland Security are placed in the care of the Office of Refugee Resettlement as they await their immigration proceedings.

The ORR then places the children in what the office calls “the least restrictive setting that is in the best interests of the child.” That placement varies based on the unique details of each case, according to the office’s website.

Editor’s Note: A previous version of this article incorrectly noted that the number of unaccompanied minors apprehended by Customs and Border Patrol in the last fiscal year was 15,000.