The House Oversight and Reform Committee has opened an investigation into the medical care of immigrant detainees in the wake of a BuzzFeed News investigation that revealed a series of allegations of substandard care from a whistleblower.

The congressional committee issued letters on Monday demanding a series of documents from Department of Homeland Security and Immigration and Customs Enforcement officials.

The letters — sent to Matthew Albence, acting ICE director, and Cameron Quinn, the DHS officer for Civil Rights and Civil Liberties (CRCL) — request the memo documenting a series of allegations from a whistleblower that was reported by BuzzFeed News on Dec. 12, along with any other documents related to the report by Jan. 10.

“The Subcommittee on Civil Rights and Civil Liberties is writing to request documents and information relating to reports of gross negligence by medical staff treating detainees in the custody of Immigration and Customs Enforcement (ICE),” Rep. Jamie Raskin, the chair of the Subcommittee on Civil Rights and Civil Liberties, wrote in his letters to Albence and Quinn.

Raskin also called for documents on other allegations of improper medical care, all communications between ICE and CRCL discussing the medical care of detainees, internal death reviews, and any documents justifying personnel actions of individuals who worked for ICE and documented improper care or discussing retaliation against such an individual.

“According to the report, most, if not all, of these incidents were the result of gross negligence on behalf the ICE personnel and medical professionals tasked with caring for detainees,” Raskin said in a statement.

A DHS spokesperson said Monday that the department has already provided the committee with multiple briefings and more than 5,000 pages of documents on the matter.

"DHS is committed to the highest standard of care," spokesperson said in a statement. "We have more than 200 medical professionals on the border and are continually updating our policies and procedures."

BuzzFeed News first reported the memo and documented how it contained reports of detainees being given incorrect medication, suffering from delays in treating withdrawal symptoms, and one who was allowed to become so mentally unstable he lacerated his own penis and required surgery.

The whistleblower reported that three people had died in ICE lockup after receiving inadequate medical treatment or oversight, and said official reports on a fourth person’s death were “very misleading.” One man died from meningitis following “grossly negligent” care. Another killed himself after saying he would do exactly that months earlier, the whistleblower said.

In a statement on Monday, a spokesperson for DHS said the "men and women of Border Patrol are committed to the highest standards of professionalism and care and have the full support of the department."

"We are still saddened by the tragic loss of these young lives, and we continue to bolster medical screenings and care at DHS facilities on the border," the spokesperson said.

The allegations were first received by Homeland Security’s inspector general in April 2018. In July of that year, the inspector general sent the allegations to Quinn’s office.

Overall, the memo says, the whistleblower alleged that the government “has systematically provided inadequate medical and mental health care and oversight to immigration detainees across the U.S.” The memo also says the inspector general will investigate the whistleblower’s allegation that they were retaliated against for raising the issues.