In the wake of at least five children dying in US government custody in the last nine months, two nurses told BuzzFeed News immigration agents have delayed taking sick children in increasingly dire condition to a hospital near the border for treatment, putting the kids at risk of potentially severe health issues.

The two registered nurses, who have treated immigrant children at a hospital in the Rio Grande Valley, said young patients arriving in recent months are often in such poor health that they're "on the borderline" of medical staff needing to call a specialized rapid response team of doctors to prevent them from going into respiratory or cardiac arrest.

The hospital is located in the southernmost tip of Texas, an area that has recently seen some of the largest numbers of immigrant families crossing the border. The nurses spoke to BuzzFeed News on condition of anonymity out of fear of losing their jobs.

The conditions faced by immigrant children in the custody of US Customs and Border Protection have drawn concern from attorneys and advocates for years, but after the death of at least five children in US custody and an increase in families being apprehended at the border, the issue is more pressing than ever.

Recently, many of the children entering the hospital from CBP custody have suffered severe respiratory distress, dehydration, and fevers that should've prompted agents to hospitalize them sooner, one nurse said.

"In some cases they should've been here a week ago and they decided to wait until the last minute," the nurse told BuzzFeed News. "It makes me wonder what Border Patrol is doing. Why is it taking them so long to realize they need to take them to the hospital?"

Many of the younger children taken to the hospital are treated for respiratory issues, while older ones tend to be dehydrated, the nurse added.

"They're so dehydrated their lips are cracked," the nurse said.

CBP did not respond to repeated requests for comment.

US in-custody deaths and reports of deteriorating detention conditions come as authorities say they don't have enough space to hold the record number of Central American immigrant families showing up at the border.

Earlier this year, Border Patrol held hundreds of immigrants underneath a bridge surrounded by a chain-link fence topped with razor wire, forcing them to endure cold, windy nights sleeping on gravel. Hundreds of others who were held at a Border Patrol station in McAllen, Texas, said adults and children had to sleep outside on dirt and grass.

A government watchdog group found that immigrants were being detained in dangerous, overcrowded, standing room-only cells, with some standing on toilets to get breathing space. In recent weeks, reports from a Border Patrol facility in Clint, Texas, drew outrage after lawyers went public with what they saw. Attorneys described children caring for infants and toddlers, a lack of access to soap and toothbrushes, and inadequate food, water, and sanitation.

Some migrants arriving at the southern border may already be sick after making a long journey through Mexico, one of the nurses said. Others are likely to fall ill after being taken into CBP custody, where they're held in packed cells for weeks, often without access to soap, water, or the ability to sleep.

