Homeland Security Secretary Kirstjen Nielsen speaks at U.S. Immigration and Customs Enforcement headquarters in Washington, July 6, 2018. Credit: Jacquelyn Martin | AP

Homeland Security Secretary Kirstjen Nielsen will travel to the U.S. border with Mexico to personally review her department’s care of migrant children after a Guatemalan boy died on Christmas Eve after he was apprehended by Customs and Border Protection.

The 8-year-old was the second young migrant to die in the agency’s custody this month. It’s been more than a decade since a child died in CBP custody, a Department of Homeland Security official told reporters on a conference call Wednesday.

Border authorities have recently seen more sick migrants crossing into the U.S., DHS officials said on the call. They asked not to be identified discussing the issue. Six people in total have died in CBP’s custody in 2018, and the agency transfers dozens of people a day to hospitals, one of the officials said.

Earlier this month, a 7-year-old Guatemalan girl died while in U.S. custody.

CBP ordered new medical tests on all children it’s holding after the boy’s death, the agency said in a statement earlier on Wednesday. The directive will mean secondary medical checks on children in the agency’s care, including unaccompanied minors and those who arrive as part of a family unit, Commissioner Kevin McAleenan said in the statement. He said the order will focus on children under 10.

“This is a tragic loss. On behalf of U.S. Customs and Border Protection, our deepest sympathies go out to the family,” McAleenan said.

The boy’s cause of death wasn’t known, CBP said earlier. In the updated statement, they offered new details on the boy’s final days.

According to a timeline issued by the agency, the boy was apprehended on Dec. 18 at about 1 p.m. with his father 3.29 miles west of the Paso Del Norte Port of Entry near El Paso for illegal entry. After a detention in the field, the two were transported to the entry point at about 4:39 p.m., the agency said in its statement.

At that facility the two were given hot food, juice, snacks and water along with six welfare checks the agency said. On Dec. 20, they were transferred to the El Paso Border Patrol Station and provided with showers, food and water and were given 17 welfare checks through Dec. 22, the agency said.

They arrived at the Alamogordo, New Mexico, border station late on Dec. 22, where they were transferred for final processing. At about 9 a.m. on Dec. 24 an agent found the child coughing with glassy eyes and he was taken to a hospital where he was prescribed antibiotics and ibuprofen. He later appeared lethargic and was returned to the hospital due to a lack of emergency medical technicians in a CBP facility and later died.

The officials said CBP didn’t violate a court order that generally prohibits the agency from detaining children longer than 72 hours because the boy was with his father. The order only applies to unaccompanied children, the officials said.

The Department of Homeland Security Office of the Inspector General and the Guatemalan government have been notified of the death, CBP said.

The border patrol agency is also considering seeking “surge” medical assistance from the U.S. Coast Guard, and potentially requesting more aid from the Department of Defense, Federal Emergency Management Agency, and Health and Human Services to assist the U.S. Border Patrol with supplemental medical capabilities, according to the statement.

Bloomberg writer Rita Devlin Marier contributed to this report.