CBP typically detains immigrants for no more than a few days when they cross the border before either releasing them or turning them over to U.S. Immigration and Customs Enforcement for longer-term detention.
The officials said that medical workers had carried out new medical exams of nearly all the children in the care of the U.S. Border Patrol. On Dec. 23, they were transferred to the Alamogordo Border Patrol Station in New Mexico.
"We heard rumors that they could pass (into the United States)".
"These heartbreaking incidents are sadly consistent with previous reports of widespread abuse of children in immigration custody and the judgment of medical and mental health organizations that Border Patrol facilities are not adequately staffed or equipped to properly care for children", Feinstein's letter read.
DHS officials did not say how many children are now held by the Customs and Border Protection.
The Homeland Security Secretary said she had tapped the Department of Defense to boost medical staffs along the border as well as the U.S. Coast Guard Medical Corps to assess CBP's medical programs and make recommendations for improvements.
Felipe Alonzo Gomez, an 8-year-old boy from Guatemala, died in a New Mexico hospital late on Christmas Eve. Felipe was hospitalized Monday after a border agent noticed he was coughing. "He wasn't sick on the way; he wasn't sick here", she said.
But it seems likely those changes won't address the real driver of this problem which isn't just economic opportunity but a belief that having a child with them gives migrants an advantage. He was treated at the hospital earlier in the day and released but was re-admitted several hours later.
The cause of the boy's death is not clear.
With border crossings surging, CBP processes thousands of children - both alone and with their parents - every month.
White House says it didn't distribute MAGA hats Trump signed
Presenting himself as an ardent supporter of the military just days after the resignation of respected Defense Secretary James N. Presidents have shared the tradition of visiting military members around the holidays in order to boost morale.
Also this week, a funeral for seven-year-old Jakelin Caal was held in a small Guatemalan village.
Jakelin Caal's family disputed some of the government's claims about what happened leading up to her death, saying the girl was healthy and had no pre-existing conditions when she and her father made the journey from Guatemala. He was eventually hospitalized twice and died.
In November, U.S. Customs and Border Protection apprehended 25,172 family members, the highest number ever recorded, as well as 5,283 "unaccompanied minors".
DHS Secretary Kristjen Nielsen released a statement Wednesday.
"Lots of them have gone with children and managed to cross, even if they're held for a month or two".
"This is under the care and the responsibility and the custody of the United States government, and they do not meet the most minimal basic standards of humanitarian health", he said.
Nielsen also said she had asked Mexican officials to investigate "the causes of these illnesses on their side of the border and to provide medical assistance in shelters as needed".
"This changing dynamic is the direct result of obvious draw factors: an immigration system that rewards parents for sending their children across the border alone, a system that prevents parents who bring their children on a risky and illegal journey from facing consequences for their actions, an asylum process that is not able to quickly help those who qualify for asylum, a system that encourages fraudulent claims, and a system that encourages bad actors to coach aliens into making frivolous claims", she said.
She said she had reached out to McAleenan "but have not received answers to explain why these deaths occurred".
Amy Lieu is a news editor and reporter for Fox News.