Migrants detained at the border are kept in freezing cells nicknamed 'iceboxes' - here's what we know about them

• Migrants detained at the border by Border Patrol and Customs and Border Protection agents are often held in freezing, cramped facilities often referred to as "hieleras" or "iceboxes" by migrants, advocates and even their detainers.
• Women and children, including infants, are held in overpopulated cells in these facilities for days with little medical care and low temperatures. They're usually given thin foil blankets to combat the cold.
• "Hieleras" have come under national scrutiny after two Guatemalan children died while in Border Patrol custody after being detained in these centers. Earlier this year, a 21-month-old girl died two days after being released from a "hielera" in Texas.
• In the past, undocumented migrants have sued the U.S. over the conditions at the "hieleras." Most of what we know about these holding centers comes from immigrants themselves through interviews, advocates and lawsuits.