A blistering report released this week alleges that U.S. Customs and Border Protection (CBP) agents neglected and abused more than 100 migrant children who were in their custody.

The report, from the American Civil Liberties Union (ACLU) and the University of Chicago Law School International Human Rights Clinic, is based on thousands of pages of records detailing accusations from 116 unaccompanied minors, many of whom were asylum-seekers, while in temporary detention centers.

"Migrant children long have reported varied mistreatment in CBP custody, including sexual, physical, and verbal abuse, and the deprivation of basic needs such as food, water, and emergency medical care," the ACLU said in a summary of the report.

Some children accused officers of punching or kicking them and running them over with vehicles. Others described being tased and verbally abused by officers.

Children also described being deprived of edible food and water, held in freezing cells, touched inappropriately by officers and threatened with rape or death.

The report accuses the Department of Homeland Security (DHS) of violating federal law by not reporting the alleged abuses to the FBI.

The ACLU obtained more than 30,000 pages of records for its report, all of which relate to alleged abuses taking place between 2009 and 2014, under the Obama administration.

"These records document a pattern of intimidation, harassment, physical abuse, refusal of medical services, and improper deportation," the report said. "These failures have allowed a culture of impunity to flourish within CBP, subjecting immigrant children to conditions that are too often neglectful at best and sadistic at worst."

This is not the first time DHS has faced scrutiny for alleged abuse.

In 2014, DHS conducted an investigation into past allegations from the ACLU of abuse against unaccompanied minors, saying that they were "unable to substantiate any of the allegations."

But, in its report, the ACLU states that past DHS investigations "indicate systemic failures to meaningfully investigate the allegations" and have failed to take action to address the complaints.

Dan Hetlage, a spokesperson for CBP, called the ACLU report "unfounded."

"The false accusations made by the ACLU against the previous administration are unfounded and baseless," Hetlage said in a statement. "The 'report' equates allegations with fact, flatly ignores a number of improvements made by CBP as well as oversight conducted by outside, independent agencies."

"CBP takes seriously all allegations of misconduct, but without new specifics is unable to check to commence reasonable steps to examine these assertions and address the accusations levied," he added.