In 2017, the US Department of Homeland Security did not investigate hundreds of civil rights complaints about alleged detainee, prisoner, or suspect abuse filed to the agency’s oversight body, according to documents obtained by Motherboard through the Freedom of Information Act.

The complaints were filed across all of DHS’s agencies, but the news comes as Immigration and Customs Enforcement (ICE), a part of DHS, is facing a reckoning with its practice of separating parent and children asylum seekers. Previous reporting has shown that DHS—and ICE in particular—has for years investigated only a minuscule number of the overall complaints it receives; these documents show that the problem has persisted under the Trump administration.

The documents obtained by Motherboard do not make distinctions between the agencies under DHS, which include ICE, the Transportation Security Administration, the Coast Guard, and others. Although why exactly a complaint was not investigated depends on a multitude of factors, and complaints can only really be assessed on a case-by-case basis, an expert Motherboard contacted said that the lack of investigations in aggregate raises questions.

“The number of complaints that apparently went uninvestigated is quite surprising and it demands a closer look,” Steven Aftergood from the Project on Government Secrecy at the Federation of American Scientists, told Motherboard in an email.

Motherboard obtained a list of all closed complaints filed with the DHS’ Office of the Inspector General (OIG) between June 20, 2016 and June 21, 2017. The OIG is designed to provide independent oversight of the DHS, investigating fraud, waste, and abuse. The section of the document covering the first half of 2017 is around 300 pages, and includes basic information such as when the complaint was filed, the sort of issue raised, and whether any action was taken.

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Looking at only those complaints submitted in 2017, hundreds are marked as “detainee/prisoner/suspect related abuse” or similar. All of these, except a small handful, are marked as “closed not converted.” As a court explained in a lawsuit filed by the American Civil Liberties Union (ACLU) against the DHS’ Office for Civil Rights and Civil Liberties, in which the ACLU is trying to obtain the names of DHS employers accused of mistreating children, the high presence of “closed not converted” means that “virtually no investigations into the complaints took place, or at least were completed.”

And for the small number of DHS employees or contractors that were investigated in the list obtained by Motherboard, the complaints were sometimes found as “unsubstantiated.”

Last year, California-based nonprofit Community Initiatives for Visiting Immigrants in Confinement (CIVIC) obtained data showing that between 2010 and 2016, there were 33,126 reports of sexual and physical abuse in immigration detention centers, but less than 2 percent of those complaints were investigated.

Aftergood said it’s possible that some of the complaints outlined in the documents obtained by Motherboard may have been frivolous, or that they were filed without enough supporting evidence that would merit an investigation. But DHS’s OIG itself told Motherboard it does not have enough resources to properly probe every complaint.