New medical checks have been carried out on nearly every child in border patrol custody, US immigration authorities have said.
These checks follow the death of a second youngster in the agency's care in the space of less than three weeks.
An eight-year-old boy, identified by Guatemalan authorities as Felipe Gomez Alonzo, died on Christmas Eve just before midnight.
He had been in the custody of US Customs and Border Protection (CBP) with his father, Agustin Gomez, since December 18.
CBP said in a statement that an agent first noticed the boy had a cough and "glossy eyes" at about 9am on Monday.
He was taken to hospital twice that day before he died, the agency said.
The cause of death was under investigation.
Officials at the Department of Homeland Security (DHS) told reporters yesterday that almost all checks ordered in reaction to the boy's death had been completed.
Some children detained in more remote areas were re-screened by emergency medical technicians or border patrol agents, officials said.
In other places, some children were taken to medical facilities.
DHS would not say how many children were in border patrol custody and authorities have not disclosed the results of the examinations.
The agency also would not say why Felipe and his father were detained for almost a week, an unusually long time, or why they were placed back in detention, at a border patrol road checkpoint, after being released from the hospital.
Another Guatemalan child in US custody, seven-year-old Jakelin Caal, died on December 8 and was returned to her village for burial.