Transcript for Guatemalan child dies in U.S. custody

Now, to the tensions at the border with Mexico. New details emerging tonight about the 8-year-old boy dying in the custody of American border officials on Christmas eve. The second young fatality in just three weeks. The department of homeland security now launching a new policy for dealing with children under 10 at the border and now asking for help from the coast guard. Here's ABC's chief national correspondent Matt Gutman. Reporter: Tonight, border patrol launching an internal review, after another child died for the second time this month. The boy and his father were both traveling from Guatemala, they were first detained near El Paso on December 18th. On December 22nd, the pair was moved due to overcrowding. But on Christmas eve, the boy showed possible flu symptoms. At about 9:30 that morning, he was taken to this hospital and evaluated. At 1:20 he'd spiked a fever of 103, but just 90 minutes later, the hospital released him back to the border patrol, prescribing him antibiotics. That evening, border patrol agents noticed the boy had vomited, but the agency says, "His father declined further medical assistance as the child had been feeling better." Later that night, as the boy's condition worsened, he was rushed back to the hospital, pronounced dead minutes before Christmas. It's just tragic, and we're thinking about his family right now. Reporter: Democrats in the house now vowing a congressional investigation. Earlier this month, jakelin, a 7-year-old girl from Guatemala, also died while in border patrol custody. The agency telling ABC news it's in the midst of a "Humanitarian crisis," 24 hundred children attempting to cross into the U.S. Just in the month of December, mostly with their families. Crossing attempts in the El Paso region have surged ten-fold from previous years. Our stations are not built for that group that's crossing today. Reporter: Immigrations and customs enforcement also overwhelmed. This week, bussing hundreds of migrants to a local El Paso park and leaving them there. All this amidst a partial government shutdown in Washington, fueled by president trump's refual to sign a budget without money earmarked for some kind of border barrier. I can't tell you when the government's going to be open. I can tell you it's not going to be open until we have a wall, a fence, whatever they'd like to call it. Matt Gutman joins us live now. The president saying today he will visit the border before the state of the union. This has homeland security announced new medical policies for migrant children at the border? Reporter: That's right. Homeland security seems to now acknowledge that its current system at the border with that historic influx of children isn't working. Now, I spoke with the commissioner of customs and border protection overnight and he said he's ordered the mandatory medical check of all children under the age of 10 in the agency's custody. The agency is also undergoing an internal review. Tom? Matt Gutman with some new reporting tonight. Matt, thank you.

This transcript has been automatically generated and may not be 100% accurate.