The death of the eight-year-old boy is the second instance this month of a migrant child dying under US detention.

An eight-year-old Guatemalan migrant boy died shortly after midnight on Tuesday after being detained by US border agents, the Customs and Border Protection (CBP) said in a statement, the second migrant child this month to die in the US detention.

The boy and his father were in CBP custody on December 24 when a Border Patrol agent noticed the child showing signs of illness, CBP said.

The father and the son were taken to the Gerald Champion Regional Medical Center in Alamogordo, New Mexico, where the boy was diagnosed with a common cold and fever, and eventually released by hospital staff.

But later that evening, the boy began vomiting and was transferred back to the hospital. He died at the hospital shortly after midnight, CBP said, adding that the official cause of death is not known.

The father and the son were not identified, and the agency said it will release more details “as available and appropriate”.

Guatemalan officials have been notified of the death, CBP said. The Guatemalan government did not immediately respond to a request for comment.

It is the second instance this month of a migrant child dying after being detained by US border agents.

Earlier in December, seven-year-old Jakelin Caal, also from Guatemala, died after being detained along with her father by US border agents in a remote part of New Mexico.

The administration of President Donald Trump has tried to deter people from crossing the border between ports of entry to seek asylum, while at the same time restricting legal access to official ports of entry.

Trump’s immigration policies

That has created a months-long wait for asylum applicants, including those who formed part of a large ‘caravan’ of Central Americans this year.

Caal’s wake was held on Monday, Christmas Eve, in her family’s village.

Her death led to criticism of President Trump’s immigration policies by Democrats and migrant advocates. But the Trump administration said Caal’s death showed the danger of her journey and the family’s decision to cross the border.

Caal’s death is being investigated by the Department of Homeland Security’s inspector general, which looks into accusations of misconduct by the agency’s employees.

CBP said on Tuesday that the Guatemalan boy’s death is being reviewed by the agency’s Office of Professional Responsibility and that the inspector general has been notified of the death.

It was not immediately known if the watchdog would open an investigation into the boy’s death.