A group of Democratic senators led by Elizabeth Warren (D-Mass.) sent a letter Tuesday night to the Department of Homeland Security and U.S. Immigration and Customs Enforcement to shut down four private detention centers.

The letter, first reviewed by HuffPost and signed by Sens. Alex Padilla (D-Calif.), Ed Markey (D-Mass.), Ron Wyden (D-Ore.), Jeff Merkley (D-Ore.), Bernie Sanders (I-Vt.), Peter Welch (D-Vt.), Cory Booker (D-N.J.), Ben Cardin (D-Md.) and Mazie Hirono (D-Hawaii), targets facilities in New Mexico, California, Louisiana and Virginia. All of the facilities have faced serious complaints over treatment of detainees. Contracts for two of those facilities are up for renewal this week.

We do not support a system that detains people in inhumane conditions that result in long-term medical issues, psychological trauma, and sometimes death. We urge that these facilities be shut down, in a step towards building an immigration system that welcomes and respects migrants, read the letter.

The letter, addressed to Secretary Alejandro Mayorkas and Patrick Lechleitner, the acting director of ICE, also demands immigration officials to hand over a list of all public and private ICE detention facilities as well as a timeline for ending contracts at those four facilities.

After reports of inhumane conditions, including sleep deprivation, dirty drinking water, and psychological trauma, independent watchdogs and other experts have recommended that the Biden administration close the worst of these facilities, Warren said. This would be a meaningful step toward ending the federal governments reliance on private detention centers.

Neither agency responded to HuffPosts request for comment.

ICE uses at least 110 detention facilities across the United States to collectively detain 36,000 to 40,000 individuals. In March, President Joe Biden increased funding for immigrant detentions, which sparked sharp criticism by dozens of advocacy groups who say he has gone back on his campaign promise to end for-profit detention facilities.

No business should profit from the suffering of desperate people fleeing violence, he said on his campaign website in 2020. Biden will ensure that facilities that temporarily house migrants seeking asylum are held to the highest standards of care and prioritize the safety and dignity of families above all.

But little has changed about for-profit detention centers since Biden took office. Instead, he has steadily increased ICE funding, which stands at more than $3.4 billion in 2024 .

All four detention centers listed in the letter faced accusations of human rights violations. Several Venezuelan detainees filed a class-action lawsuit last year alleging unsanitary conditions at the Torrance County Detention Facility in New Mexico and said they were denied medical care, access to working showers and adequate food. In Louisiana, detainees said the facilities were overcrowded and unsanitary . Similar abuses have rocked the detention centers in Virginia and California .

Every immigrant deserves to be treated with dignity. Upon termination of contracts, ICE should pursue community-based alternatives to detention, which provide immigrants with resources that help them integrate into their communities and stay with their families, continued the letter.