When they were apprehended in a remote desert area near the New Mexico border around 9 p.m. on December 6, officials said, the girl was assessed to be in good health and the father signed a form saying she was not sick.
Homeland Security said she started having seizures more than eight hours later. She was airlifted to a hospital in El Paso, where she went into cardiac arrest, was revived, and died less than a day later.
The DHS Office of the Inspector General announced an investigation into the girl's death on Friday afternoon, with the results to be reported to DHS Secretary Kirstjen Nielsen, Congress and the public. "It took a such a large crowd, it took our Border Patrol folks a couple times to get them all".
Nielsen said Jakelin Caal Maquin's death was "heart-wrenching" and said her heart goes out to the child's family. Normally, agents offer food and water to people when they take them into detention.
The figure represents migrant deaths recorded by border officials within their area of responsibility and is not exclusive to people in US custody. The statement also expressed sympathy for the family.
"It's a needless death and it's 100 percent preventable", he told reporters.
They were about 90 miles north of the border around December 6 when they turned themselves in to three Border Patrol agents.
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But Mr Juncker criticised Britain's lack of clarity over what it was seeking from the future relationship. This was a Tory party internal procedure, triggered by members of her own parliamentary group.
At 6:35am, more than eight hours later, the girl began to have seizures.
Democratic Congressman Joaquin Castro, whose district is just outside San Antonio, Texas, said in a statement that he would request that Congress investigate Caal's death. "But again I can not stress [enough] how risky this journey is when migrants choose to come here illegally". "Border Patrol always takes care of individuals in their custody and does everything in their power to keep them safe". She said the girl's group was 145 kilometres from where it could be processed and a few trips were needed to get such a large group over to processing. Once again, we are begging parents to not put themselves or their children at risk attempting to enter illegally.
The child's death came as President Donald Trump struggles to deter a tide of migrants fleeing poverty and violence in Central America - and battles with Congress for a budget to build a massive wall across much of the US-Mexico Frontier.
A Department of Homeland Security representative said an autopsy would be performed but the results could take weeks.
An initial cause of death was listed as "septic shock, fever and dehydration" by physicians at El Paso's Providence Hospital.
A seven-year-old Guatemalan girl died in American custody after being detained by United States border police in New Mexico, The Washington Post reported has reported. He issued a statement declaring, "This is a humanitarian crisis and we have a moral obligation to ensure these vulnerable families can safely seek asylum, which is legal under immigration and worldwide law, at our borders".
"This tragedy represents the worst possible outcome when people, including children, are held in inhumane conditions", the statement said.