CHICAGO — Abner, a 17-year-old Guatemalan boy, vividly recalls the first 48 hours he spent inside the U.S. Border Patrol station in Yuma, Arizona. He was awake for all of them because there was no space to lie down.

Packed into a cell with other migrant boys, Abner said the older children would give the 8, 9, and 10-year-olds space to lie down on the floor while they would try to sleep sitting or standing up. With nothing to cover him, Abner would tremble.

"I had to stay almost two days like this, standing. I didn't sleep. And they didn't treat me well because I would ask for at least food or water or something to cover myself with and they would deny it," Abner told NBC News in Spanish.

Abner said he and other older migrant kids jammed into a cell at the Yuma border station would give younger kids space to lie on the floor while they slept sitting or standing up. NBC News

Eventually, he learned to sleep on a pile of trash in the corner of the cell, said Abner, who does not want his full name or his face used out of fear he will be targeted for deportation.

Earlier this month, NBC News reported that children held at the Yuma station between April and June had told government case managers about overcrowding and poor conditions, including retaliation for complaints, at least one sex assault and sleeping on concrete.

In total Abner spent 11 days from late May to early June in the Yuma border station. He describes them as filled with hunger and thirst, extreme temperatures and fear of the guards manning the facility. They refused to give him food when he asked, mocked him if he asked what time it was, and, on one occasion, punched another boy in the stomach, Abner said.

"With a punch they knocked the wind out of him ... But I don't know why," Abner said, describing what he said happened to the 16-year-old.

Abner said he and his cellmates were only fed twice a day, leading him to become very hungry.

"They would give us (food) around 10 [a.m.] and around 5 [p.m.], around that time," he said. "After that, they wouldn't give us anything. And I would get hungry at night and they wouldn't give us anything. We would ask but they wouldn't give us." he said.

The older boys in Abner's cell learned to protect the younger children, whose cries would anger the guards.

"Sometimes, we would give one [hamburger] to the little ones. Because the little ones were the ones that wanted to eat more than others. At least, [the older kids could] stand the hunger a little more," Abner said.

The U.S. border station in Yuma, Arizona. NBC News

For water, they had only the sink in their cell, and they had no hand soap. They drank from the sink by cupping their unwashed hands.

Abner said he lost track of whether it was day or night because the lights were always on in his cell and they were yelled at for going near the windows.

"Sometimes we would ask what time it was and they would tell us, 'Oh do you have a meeting to go to?' And they would reprimand us on why we were asking," Abner said.

A Customs and Border Protection official told NBC News that Abner's claims "are inconsistent with CBP’s records corresponding to the juvenile migrant’s time in custody from May 25 to June 5, 2019."

Said the official, "CBP processing and notification to the Office of Refugee Resettlement (ORR) were completed the day following his apprehension, on May 27, and he remained in CBP’s custody until ORR placement was provided on June 5. It is important to note that CBP takes all reports of employee misconduct seriously and the juvenile’s allegations of mistreatment have been referred to CBP’s Office of Professional Responsibility."

Overcrowding of children in border stations has decreased since June, with more funding for detention space and a drop in immigrants crossing the southern border overall. Acting Department of Homeland Security Secretary Kevin McAleenan was asked about the poor conditions in border stations at a Congressional hearing last week, and he said agents did the best they could under the conditions.

A group departs U.S. Border Patrol vans in Yuma, Arizona, on June 3, 2019. Randy Hoeft / Yuma Sun via AP

After leaving the Yuma station, Abner was held at a facility run by the Department of Health and Human Services, where he recalls playing soccer and making friends. He is now reunited with his father in Chicago and waiting to hear from his lawyer about the next step in his court case.

His father said that when he first saw Abner at Chicago's O'Hare airport during their reunion, "My heart flew out of my body."

Abner has four sisters back in Guatemala. He wants them to come to the United States to escape extreme poverty, but he worries about them experiencing the treatment he says he experienced at the hands of Customs and Border Protection.