WASHINGTON — The poor treatment of migrant children at the hands of U.S. border agents in recent months extends beyond Texas to include allegations of sexual assault and retaliation for protests, according to dozens of accounts by children held in Arizona collected by government case managers and obtained by NBC News.

A 16-year-old Guatemalan boy held in Yuma, Arizona, said he and others in his cell complained about the taste of the water and the food they were given. The Customs and Border Protection agents took the mats out of their cell in retaliation, forcing them to sleep on hard concrete.

A 15-year-old girl from Honduras described a large, bearded officer putting his hands inside her bra, pulling down her underwear and groping her as part of what was meant to be a routine pat-down in front of other immigrants and officers.

The girl said "she felt embarrassed as the officer was speaking in English to other officers and laughing" during the entire process, according to a report of her account.

A 17-year-old boy from Honduras said officers would scold detained children when they would get close to a window, and would sometimes call them "puto," an offensive term in Spanish, while they were giving orders.

Earlier reports from investigators for the Department of Homeland Security's Office of the Inspector General from the El Paso and Rio Grande Valley sectors in Texas detailed horrific conditions for children and other migrants held in overcrowded border stations where they were not given showers, a clean change of clothes or the space to sleep. The reports from the Yuma CBP sector describe similar unsanitary and crowded conditions but go further by alleging abuse and other misconduct by CBP officers.

President Donald Trump has pushed back against reports of poor conditions for children, and Kevin McAleenan, acting secretary of the DHS, which oversees CBP, has said the reports are "unsubstantiated."

In a statement about the Yuma allegations, a CBP spokesperson said, "U.S. Customs and Border Protection treats those in our custody with dignity and respect and provides multiple avenues to report any allegations of misconduct. ... The allegations do not align with common practice at our facilities and will be fully investigated. It’s important to note that the allegation of sexual assault is already under investigation by the Department of Homeland Security’s Office of Inspector General."

Ken Cuccinelli, acting director of U.S. Citizenship and Immigration Services, said Wednesday that the allegations are under investigation and will face multiple reviews.

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"Anyone involved in sexual assault or physical harassment like that I would, of course, expect to be fired, not merely disciplined," he said on MSNBC.

The DHS had been sounding the alarm on overcrowding in border facilities for months, resulting in a $4.5 billion emergency funding bill recently passed by Congress. In Yuma, a soft-sided tent facility was opened at the end of June to accommodate overcrowding at the border station.

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But in almost 30 accounts obtained from "significant incident reports" prepared between April 10 and June 12 by case managers for the Department of Health and Human Services, the department responsible for migrant children after they leave CBP custody, kids who spent time in the Yuma border station repeatedly described poor conditions that are not pure byproducts of overcrowding. They reported being denied a phone call, not being offered a shower, sleeping on concrete or outside with only a Mylar blanket, and feeling hungry before their 9 p.m. dinnertime.

One child reported "sometimes going to bed hungry because dinner was usually served sometime after 9 p.m. and by that time she was already asleep," according to the documents.

All children who gave accounts to case managers had been held at the border station longer than the 72 hours permitted by law.

Laura Belous, an advocacy attorney for an organization that provides legal services to migrant children, the Florence Immigrant & Refugee Rights Project, said her group was "horrified and sickened by the allegations of abuse ... But unfortunately, we are not surprised."

"The children that we represent have reported being held in overcrowded and unsanitary conditions for days," Belous said.

"Our clients tell us that they have seen CBP agents kick other children awake, that children do not know whether it’s day or night because lights are left on all the time, and that they have had food thrown at them like they were wild animals."

"Our clients and all migrants deserve to be treated with dignity and respect," she said.

Rep. Matt Gaetz, R-Fla., said Wednesday that he had visited the Yuma border station in April "and the human condition that I observed in Yuma was the worst state of the human condition I have ever seen in my life." But Gaetz also said, "I could tell you that the Border Patrol agents and the Homeland Security agents that were there were dealing with conditions that they had not trained for, they were not equipped to handle, and they were doing the very best they could under terrible circumstances."

Nearly every child interviewed by the HHS case workers after leaving the Yuma border station reported poor sleeping conditions. A 17-year-old boy from Guatemala reported having to sleep outside even though his clothes were wet from having recently crossed a river, likely the Colorado River.

Once he was transferred inside, the conditions were not much better. "He shared that there was not always space on the floor as there were too many people in the room. He further shared that there would be room available when someone would stand up," his report stated.

Many migrant children said they were either not given a mattress, a pillow or a blanket, or were just given a Mylar blanket instead.

A temporary holding facility for migrant children in Yuma, Arizona. NBC News

Other children described being scared of the officers and said the officers would get angry if they asked for anything. One child wore soiled underwear for the 10 days he was in the border station because he was afraid to ask the officers for a clean pair, according to one of the reports. Another, a 15-year-old girl from Guatemala, described the food as "gross and cold most of the time."

Health and Human Services referred NBC News to the Department of Homeland Security for comment.

In a statement, Rep. Elijah Cummings, D-Md., chairman of the House Committee on Oversight and Reform, said, "These allegations are very concerning and need to be fully investigated. The president has denied any problems with these detention centers — despite multiple confirmed reports to the contrary — but it is the Trump administration’s own policies that have contributed to this humanitarian crisis and this lack of accountability."

Cummings has called on McAleenan to testify about the poor conditions for immigrants at the border.