An eight-year-old girl has died in US Customs and Border Protection (CBP) custody after a medical emergency, the agency says.

The girl and her family were detained at a border patrol site in Harlingen, Texas when she fell ill, the CBP said. 

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. 

The Honduran consul in the border town of McAllen, Texas, José Leonardo Navas, identified the girl as Panama-born Anadith Tanay Reyes Alvarez. 

Mr Navas told the Associated Press that she 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. 

The government did not provide any information on the medical emergency the girl experienced or other circumstances surrounding her death. It said it would share more details as they became available. 

In a statement, the Congressional Hispanic Caucus said it has asked Homeland Security Secretary Alejandro Mayorkas to brief lawmakers on the incident. 

"We have a fundamental duty to protect migrants in our case and custody, any death is unacceptable," the statement said. "We cannot go back to 2019." 

It comes shortly after the expiration of Title 42, a Covid-19-era border policy that allowed the US to quickly expel migrants who crossed into the country illegally. 

Border officials had been bracing for a sharp rise in migrant crossings in the wake of its expiration, though initial data shows US officials saw a much smaller surge than expected.