An eight-year-old girl died while in US Customs and Border Protection custody after a medical emergency.
The girl and her family were detained at a border patrol site in Harlingen, Texas when she fell ill.
The agency said she was transported to a local hospital where she was pronounced dead on Wednesday.
It said it would investigate the incident and that the Department of Homeland Security had been notified.
Authorities say the girl was travelling to the US with her Honduran parents and her two older siblings, and had been born with heart problems.
Her father reportedly told the consul that she had been operated on in Panama three years ago.
Her death appears to be the first in US Border Patrol custody for several years.
But it is the second death of a child from Latin America in US government custody in as many weeks.
Last week a 17-year-old Honduran boy who arrived unaccompanied in the US died at a government shelter facility in Florida.
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