A group of more than 100 congressional Democrats demanded Thursday that U.S. Immigration and Customs Enforcement release female detainees from a Georgia detention facility who allege they received subpar gynecological care while detained there.

The lawmakers say the women may be potential witnesses in an ongoing federal investigation into Mahendra Amin, a physician who the women allege conducted “nonconsensual and medically unnecessary” gynecological procedures on female detainees at Irwin County Detention Center. Their letter calls for the women to receive necessary certifications for a chance to apply for U-visas, which allow undocumented immigrants who have assisted law enforcement to apply to stay in the country legally.

Amin “flatly denies” the allegations, his lawyer, Scott R. Grubman, said in a statement.

“Dr. Amin has always treated his patients, including those who were in ICE custody, with the utmost care and respect,” Grubman said.

Attorneys for the women allege that ICE has been trying to deport many of them before they can finish helping investigators, including as recently as this week. At least three federal lawsuits have been filed on behalf of three of the women who say they were nearly deported, arguing that ICE would be retaliating against them and violating their First Amendment rights if the deportations are carried out.

“Deporting these witnesses — especially when none of them have received independent physical or mental health evaluations by medical experts — amounts to a de facto destruction of evidence,” wrote the lawmakers, including Senate Minority Leader Charles E. Schumer (D-N.Y.).

The letter was addressed to acting ICE director Tony Pham as well as the three federal offices — the Justice Department, FBI and Department of Homeland Security’s Office of the Inspector General — conducting the probe, which was first opened in September.

ICE spokeswoman Danielle Bennett said in a statement to The Washington Post that ICE was “fully cooperating” with the investigation, including accommodating interviews for the probe and notifying the investigators about any plans to deport or transfer Amin’s former patients. She added that the agency does not comment on ongoing litigation and responds to congressional letters through official channels.

“Any implication that ICE is attempting to impede the investigation by conducting removals of those being interviewed is completely false,” Bennett said.

A request for comment to the Justice Department was referred to the U.S. attorney’s office for the Southern District of Georgia, which declined to comment. Neither the FBI nor DHS’s Office of the Inspector General responded to emails seeking comment.

The U-visa program, first created in 2000, is open to undocumented immigrants who cooperate with law enforcement after witnessing or being victim to a violent crime. Individuals can receive temporary legal residency and a path to U.S. citizenship, though in recent years the program has seen a growing backlog and a decline in applications.

Elora Mukherjee, a Columbia Law School professor, said that certification for such a visa is the “basic minimum protection” that federal investigators can grant to the detainees who are willing to cooperate with their probe.

“These women are taking enormous risks to try to do justice to what happened to them,” she said in an interview, “and everyone in the investigation team should make sure that as many women as possible come forward and speak out.”

The letter from congressional Democrats also demanded that investigators establish a “clear and transparent process” for women detained at Irwin to identify themselves as witnesses and commit to interviewing all women who “credibly” allege medical abuse. In addition, the lawmakers wrote, any woman making allegations to investigators should be allowed to reenter the country and apply for a U-visa as well.

National attention descended on Irwin in September, after a whistleblower report by a nurse at the facility, Dawn Wooten, alleged that a doctor — later identified as Amin — was subjecting immigrant detainees to unwanted hysterectomies.

Her claims about widespread unwanted sterilizations quickly came under scrutiny. The hospital where Amin practiced said just two women in ICE custody had been referred for hysterectomies.

Allegations against Amin nonetheless generated significant attention from lawmakers, news organizations and human rights groups. As The Post’s Maria Sacchetti reported, an independent team of medical experts, including nine board-certified obstetricians, reviewed more than 3,200 pages of medical records from 19 women at Irwin who alleged mistreatment. They found what they consider to be a troubling pattern of inadequate care that included incorrect diagnoses and a failure to secure informed consent for surgery and other procedures.

The DHS inspector general initiated its investigation in late September. In the weeks since the probe began, the lawyers allege, ICE has moved to deport several of the women who raised the alarm, including Ana Adán Cajigal, who has often been at the forefront of those speaking out. From inside the facility, the 25-year-old spoke to investigators and lawmakers, and often acted as a translator between lawyers, reporters and other detainees.

Adán, who has been detained at Irwin for more than eight months, said she was examined by Amin on Sept. 14 for what she thought may have been a venereal disease. Allegedly, Amin silently and forcefully inserted a camera into her vagina without lubrication and ignored her signs of distress. He told her she needed birth control pills for a cyst the size of a toenail on her left ovary. But when she was taken to a different doctor weeks later, they told her she had no such cyst, she said in the lawsuit.

About two weeks later, Adán was ordered deported. But it was not until Tuesday — nine days after her interview with investigators — that ICE abruptly notified her she would be deported to Mexico the next day. After a team of lawyers intervened at the last minute, Adán is now suing ICE after nearly being deported. The lawsuit is a last-ditch effort to prevent her own deportation.

At least two other women have filed lawsuits following similar incidents. Adán’s story, her lawsuit said, “fits into a pattern of swiftly deporting witnesses once they identify themselves as willing to exercise their First Amendment rights to testify.”

Grubman denied all allegations of wrongdoing by Amin, noting that his client operates outside the ICE facility and is not involved in immigration proceedings. He said that his client “has and will continue to fully cooperate” with the ongoing investigations and is “confident that he will be completely exonerated.”

Maria Sacchetti contributed to this report.