Immigrant families are being detained at the Karnes County Residential Center in Texas. Getty Images

House Democrats have condemned the Obama administration's policy of detaining immigrant families in what critics say are unsafe and even abusive detention centers, a program the Department of Homeland Security has claimed was designed to deter other immigrants from entering the U.S. illegally. The centers were the result of last year’s crisis at the U.S-Mexico border in which a surge of immigrants, the majority of whom were children, sought entrance into the U.S.

Tens of thousands of women and children have been kept in detention centers in Berks County, Pennsylvania, Dilley, Texas and Karnes, Texas, since the summer of 2014 with few answers and little idea as to when they could be released. “We have heard horrific stories of sexual assault, intense physical violence, kidnapping and sex trafficking,” the Democrats wrote in a letter addressed to Homeland Security Secretary Jeh Johnson, according to the Hill. Among the 135 lawmakers who signed the letter were Minority Leader Nancy Pelosi, D-Calif., and Democratic Whip Steny Hoyer from Maryland.

“These stories come not only from adult mothers, but also from young children who have been victims of such abuse,” the letter read. Lawmakers said the psychological states of many women and children were deteriorating as they waited for their cases to go before immigration courts. They claimed most of the detainees, the majority of whom are from El Salvador, Guatemala, and Honduras, were fleeing violence in their home countries and that being detained would only exacerbate past traumas.

The DHS has previously disputed reports of sexual misconduct at its detention centers following an investigation into several complaints from immigrants detained in Texas.

Reports of overcrowding and unsanitary conditions have led human rights groups to criticize the Obama administration’s so-called lock ‘em up approach. Such groups have cited stories of mothers suffering from trauma, depression and even suicidal thoughts as a result of the uncertainties they’ve faced. Many of the families were seeking asylum in the U.S., but have since spent almost a year in legal limbo since being detained in July 2014, according to Human Rights Watch.

Pressure has mounted in recent months to close the detention centers. Hundreds of protesters gathered in Dilley, Texas earlier this month to call for the closure of the South Texas Family Residential Center. Immigrant rights groups have flooded the White House with letters demanding that President Barack Obama end the detentions.

"By rendering parents as helpless as their children, the camps both undermined family structures and created a constant undercurrent of anxiety," American Civil Liberties Union attorney Carl Takei wrote of the conditions in the detention centers. "Today, immigration authorities under President Obama's direction are needlessly inflicting the same trauma on families that arrived in the United States seeking protection."

Among the other high-profiled Democrats to speak out against the detention centers was former secretary of state Hillary Clinton, who has said there should be a “more humane” way to house immigrant families. Clinton said she was "very worried about…detention facilities for people who are vulnerable and for children.”